HELP !!

[jeanettetherese.livejournal.com]

My boyfriends mom gave me her old sewing machine... which is a really old kenmore... and im trying to run a straight stitch into some stretch fabric... but I dont know what tention to use... I tried diff ones and the first few times the thread came loose and came out of the needle... and the second times it would get all knotted up in the bobbin hole ??? ADVICE ANYONE !!