Getting overlocker tension right

atm i just wing it and if it looks ok i'm happy but sometimes i know it's not but don't know how to fix it!

Does anyone know of a dummy's explanation for overlocker tension?

All the diagrams i have found are in b&w which really doesn't convey the info well.

tia!

I don't know, but I want to. LOL, so I'll be watching this thread. I have an instruction manual for mine, but still can't get it right (probably doesn't help that I'm primarily sewing with voile which is incredibly lightweight)