[brother ls 2129]

hello there! Ive been lurking at crafster for awhile now and i just finally got a sewing machine last week.
i was soo happy, i bought a brother ls 2129 sewing machine, and well my problem is that i think I'm threading it incorrectly.
you see when i try sewing something, the thread wont stay in the material, the minute the needle comes out so does the thread. I'm using the upper needling threading thing since i cannot for the life of me understand the lower bobbin threading nor do i know the difference.
My mother hasn't sewn since highschool so she cant remember.
so i was looking for a better explain or some advice.
thanks in advance!