OK, run the top knob all the way to the red dot. That should be "0" width or straight stitch. Then turn the stitch length knob off of the B in the square. That is most likely a setting for button holes. Set it over on one of the numbers, that should give you your straight stitch setting.
Kenmores are great machines but I've found you need to have a manual to get the settings exactly right.
I looked this one up on the Sears site and they didn't list a manual. But Relics does have it listed
{
http://pages.sewing-machine-manuals....e/1434292.html } Not free, but when you have a good machine the extra cost of a manual is worth it.
Joe