How do I fix loose stitches without having to start over?Loose on the left hand border. I now how 6 by 4 foot . Just learned how to crochet 3 weeks ago by watching a video. Help !!

The tension on the thread is too loose. However, first, verify that the thread is completely seated in the tension mechanism. When threading every thread on your machine, make sure the presser foot is always UP. When threading each thread, give each an extra little tug when going through the tension mechanism--sometimes you will hear the thread pop when it seats. A thread that is not seated will not have the correct tension applied, so the stitching will be loose and loopy.

hi linda.
not sure if this link will help you out but have a look.
Viking 1 sewing machine the needle and presser foot bar is loose how can...

It's a double crochet but goes around the post instead of in the top of the stitch.

How to Work Front Post Double Crochet Stitches dummies

Have niece sit in front of mirror and you watch mirror, not her. Should reverse left and right. That's how my grandmother taught me. We giggled a bunch, but I finally got it...

Are you 100% sure you are using the right size bobbin?

It appears that there are two issues: skipping stitches, and, loose stitches. Let's deal with them individually but first some general points to check.
1. Change both needles for completely fresh ones out of the package. Make sure that they are inserted all the way up, this is very important. The right needle should appear longer than the left one. Make sure also that you are using the correct needles for your serger.
2. Use a good quality thread with very little stretch, almost no fuzzies, and in pastel colour. Dark thread ages quicker, therefore has a shorter shelf live. A good quality sewing machine thread is also acceptable.
3. Make sure that the tension dials are clean and free of lint or other debris.
4. Re-thread the serger in this order, keeping the presser foot in the down position at all times
a) Upper looper. Ensure that the thread is securely embedded inside the tension discs. Place the thread tail under the presser foot to 11:00 o'clock and place the presser foot down again
b) Lower looper. This is the difficult one to thread but make sure that all the thread guides are properly threaded as well as the upper looper elbow. Check that the thread is lodged between the tension discs. Once the lower looper eye is threaded, place the thread in front and over the upper looper and then under the presser foot to 11:00 o'clock and place the presser foot down again.
c) Right Needle. Thread the right needle path, again ensuring that the thread is between the tension discs. Place the thread tail under the presser foot to 11:00 o'clock and lower the presser foot.
d) Left Needle. Proceed as with left needle.
e) Double check that all tension dials have their respective threads embedded between the discs by pulling firmly up on each thread above the tension dials.
f) Check that the stitch length is set to between 2.5 and 3.0, differential to normal, blade position to middle, blade is engaged, and upper looper converter not in use.
g) Set tensions to recommended setting for 4-thread overlock.
g) Make a test stitch out. How is it? Still having the same issue/s?
If yes, continue with the items listed below, otherwise have a great time serging.

Skipping Stitches:
1. Check that the looper tips are smooth. Burrs will cause problems.
2. Check that the needles match the type of fabric being sewn.

Loose Stitches:
1. Double check threading.
2. Debris caught between tension discs will also manifest itself in loose stitches. Take an 8" X 6" piece of medium weight clean and lint free cotton fabric, fold it in half length-wise and pass the fold only firmly between the tension discs from top to bottom (with the presser foot up and no thread in the tension dials).

Re-thread and test stitch. How is it now?

After the Shell row... chain 2,skip 1, then begin your double crochet.

May I suggest that you find a crochet forum or video on youtube? Lots of things to learn on Youtube. ;)

You should not have to adjust the bottom tension when using sewing thread.

There is a tiny screw on the side of the bobbin case - left/loose; right/tight.

Mark the screw head slot and edge of the bobbin case with nail polish or sharpie so you know where you started.

If you are having a stitching problem that appears to be loose bobbin thread, it may be that the machine was threaded with the presser foot down.

Always thread a sewing machine with the presser foot up.

When the presser foot is down when threading, the thread cannot enter the tension control and you get loose, loopy stitching.

Could be a tension issue.

Try this to see if it helps:
Remove top thread.
ALWAYS RAISE the presser foot and rethread from the beginning.
Start the top tension set at the midway point and then adjust.
Check that the bobbin is threaded and installed correctly.

Understanding Thread Tension Threads

Sewing Lesson 10 How to Fix Tension on Your Sewing Machine