I have a Singer 237, great machine.
When you put the hand wheel back on, make sure that the stop motion washer has the ears out. Oil the shaft that the hand wheel goes on, also put a bit of oil on your finger and run it around the inside of the hand wheel.
There is a free manual for the 237 at Singerco.com. Click on the Support tab, then manuals and then type in 237 and it will come up with your manual. You can download it and then print it.
Sharon in Texas