How to put the flat side of needle on handy stitch machine?

It is skipping stitches.

Use a brand new needle that is a suitable type for the fabric and thread you are sewing. If sewing knit, use a ball-point needle. If sewing woven fabrics, use a sharp needle (ie universal,
Use good quality sewing thread--no old or bargain bin variety.
Be sure to install the needle facing the correct direction. On most machines, the flat side of the needle faces the back of the machine, however, if the bobbin loads on the left side (not from the front), the flat side should face the throat of the machine.
There could also be a burr somewhere that is catching the thread and causing the skipped stitch.

What to Do If Your Sewing Machine Is Skipping Stitches

Basic Maintenance Tension Skipped Stitches

https://fashion-incubator.com/10_reasons_for_skipped_stitches

All About Needles SCHMETZ Needles

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You need to change the correct size needles. There are two types of needles. One with cylindrical head and other with cylindrical head with flat surface on one side.
The other problem may be the position of the direction of the thread passing through the needle.
The third problem may be move your needle position one millimeter up or down and tighten it and check.
Please follow through these 3 steps one by one. You can fix the problem

Check your manual for the "System" of needle
a normal sewing machine needle has a "System" or dimension
called 15x1 or 705 H. That indicates the length, the circumference
etc. If the needle you received with the machine is the same length as the above system then you should be ok. Also most often the needle package for most machines will be labeled "Universal"

Skipped stitches

1. The needle is not inserted correctly

Remove needle & reinsert needle( flat side towards the back of machine)

2. The needle is damaged

replace with new needle

3. The wrong size needle is being used

Choose a needle to suit the thread & fabric

4. The foot not attached correctly

Check & attach correctly

Have you fixed a new needle. If so check you fixed it right way. Usually the flat side of the needle goes to the Rod side.

Skipped stitches
1. The needle is not inserted correctly
Remove needle & reinsert needle( flat side towards the back of machine)
2. The needle is damaged
replace with new needle
3. The wrong size needle is being used
Choose a needle to suit the thread & fabric
4. The foot not attached correctly
Check & attach correctly

Skipped stitches
1. The needle is not inserted correctly
Remove needle & reinsert needle( flat side towards the back of machine)
2. The needle is damaged
replace with new needle
3. The wrong size needle is being used
Choose a needle to suit the thread & fabric
4. The foot not attached correctly
Check & attach correctly

if the needle has a flat side then the needle goes in with the flat side facing the back of the machine

1. Loosen needle screw & insert needle with shank's flat side facing front of machine. Push needle in all the way, then tighten screw to hold needle in place.
2. Install a fully wound bobbin by loosening bobbin nut & placing bobbin on top. Re-attach bobbin nut & tighten. If standard thread spool will be used, then attach spool pin to bobbin shaft & place thread spool onto shaft. Attach white spool cap on end of thread spool, then tighten. Bobbin/spool should unwind facing forward toward needle.
3. Bring end of thread through thread guides & over tension control. Pass end of thread through needle eye, from back to front, & pull it out about two inches.
4. A spring pushes pressor foot onto fabric that is being sewn, so lift pressor foot & place fabric underneath.
5. Turn large handwheel on side of machine (handwheel can be turned in either direction) to raise needle arm to its highest position.
6. Holding the Handy Stitch in place with your right hand, press on power switch & begin sewing. Guide fabric (being sewn) with your left hand.
7. To end this sewing session, turn off power. Turn handwheel to raise needle to its highest position. Carefully pull out about three inches of thread through needle & snip, then lift pressor foot to remove fabric. Turn fabric over & loop needle threader through last stitch. Place end of thread from underside through eye of needle threader, & pull to loop through. Pull to tighten and snip end of thread.

1) It’s possible the machine is threaded incorrectly. Remove the thread completely and rethread the machine. Be sure to use good quality thread--don't buy the cheapest you can find. A good thread will help your machine perform better and your projects last longer.

2) Poor stitch quality can be caused by the needle. Make sure you're using a new needle that's right for the job. Many times machines are taken in for repairs and all they need is a new needle. If you can't remember the last time you changed the needle--it's past time. Needles should be changed at least every eight hours of sewing.

3) When inserting a new needle, make sure the flat side of the needle faces away from the bobbin area. For example, if your machine has a frontloading bobbin, the flat side of the needle faces the back of the machine. If your machine has a side-loading bobbin, the flat side faces the right side of the machine. Some older sergers require special needles that don't have a flat side. Refer to your owner's manual to properly install a serger needle.

4) Thread that shreds or breaks can be blamed on the needle. Use a good thread and make sure the needle eye is large enough for the thread type. Also use the right type of needle for the fabric;
5) The machine tension adjustments put stress on the thread so it doesn't simply flow through the machine. When the upper and lower tensions are balanced, the stitch forms correctly. Tension is easy to adjust--stitch on fabric samples with a different thread colour for the upper and lower threads. Observe the stitch, adjusting the tension until the stitch is formed correctly. As a general rule, adjust the upper tension first. If the stitch still isn't right, adjust the bobbin tension.