How can I adjust the height of the handel bars on my Schwinn Sprint 10-speed?

There should be a large adjuster knob located on the right side of the bike at the base of the seat post. Usually where the seat post meets the main body of the bike. Ive included a link to a web page for an owner's manual. Try page 11 and the marker labelled 'P'.
Some bikes have the height adjuster set on the front of the seat post tube, directly under the saddle.
https://download.nautilus.com/supportdocs/AM_OM/Schwinn/SCH.130-170.MY13.SM.EN.pdf

loosen of the handle bar stem from the front forks and turn to square to the wheel then re-tension the bolt/s

It sounds like possibly a mish-mash of parts. No such thing as a 3sp track bike, although there were 3 speed fixed gear hubs. Without a picture it's not easy to help further.

I’m happy to help further over the phone at https://www.6ya.com/expert/donald_f2ed37026a3ac881

Its an internal code used in manufacture

I'm answering 7 years later. I have a Schwinn Varsity 2500 Bike made probably in 2015. The Schwinn Varsity Bike is not set up the same way as a traditional bike. I loosened the center compression bolt and the two side stem clamp bolts and it came loose where I can adjust it up or down but, there's nothing to tighten the slack up below. I did some research. My original post here was to add or remove a spacer. I think you can remove a spacer to lower but, I don't think the stem is long enough to add another one. I've seen they sell an extension that you can add-on to make the handle bars higher.

http://www.sheldonbrown.com/handsup.html

A major limitation is the steerer tube length. No matter how many times you cut a steerer tube it won't get longer.

Getting Riser Bars or simply flipping the stem over or getting one with a different rise and reach might give you the added height you need. If you LIKE the handlebars, the stem is the best and least-invasive option as most new ones come with front loaders (detachable front caps) that allow replacement without stripping components off one side of the handlebar. In minutes a Bicycle Shop could swap any number of them onto your bike for you to try.

A reputable Bicycle Shop would have fit the bike to you before you took it home.

In order to raise the handle bars, you will need a hex key. Put it into the hex indentation at the top. Turn it left to loosen it. Then raise the handle bars to the desired height.

There are 2 nuts on the bar from footrest to gear-change, 1 has a right-hand thread & the other has a left-hand thread.
Undo them both then turn the bar to alter its length thereby raising & lowering the gear-change height

Ride safe
Bike-Doc
Please mark this as very helpful (if it has been!!)

there is a nut on the lower part of the hadel bars you loosen that up then rais handel bars.

The presser bar is not moving, there is a set screw that controls the presser foot height on the bar, it may be to tight. Take the side cover off, and look for the presser bar, the set screw unit should be facing you. Unscrew it and see if the presser bar handel will now move.

The presser bar height should be set at 7 mm. To make an adjustment loosen the set screw. From the top of the machine, press down firmly on the presser bar and then secure the set screw.