singer 5528 is eating my bobbin thread!!!?

i think it's a tension problem but i have no idea how to fix it. it's an old-school machine and way out of my comfort zone. i usually use a Janome memory craft 4000. but i found this singer 5528 at a thrift store for $30 and couldn't resist. actually, the janome is eating the thread, too. i was sewing along just fine and it suddenly keeled over on me (jersey knits are a pain). so, i guess my question is "how do you change the tension on just about any machine?" oh, and what's the proper thread pattern for the singer 5528? 'cause i'm not sure i got that right either. also, i'm having trouble getting it to sew at all. it'll go down, but it won't go back up. there are two knobs on the side (one inside the other) and they lock together to stitch, and then you unlock them to do a bobbin, right? well, i can't get mine to work right. any suggestions? TIA