Mary Kay -- a belated reply -- if you haven't found the self-threading needles yet, I got mine at the hardware store, of all places -- Ace Hardware.
I rather think they were Singer brand, but, in any event, they were discovered hanging in a small display of assorted basic sewing notions.
And yes, you want both the top and bottom threads involved -- bring both to the top of the quilt (or bottom, if you prefer) before knotting & burying. Knotting them together ensures the knot's right up against the fabric, so your last stitch won't loosen.
If you've never done this before -- to bring up the bottom thread, pull gently on the top thread. The bottom thread should appear as a little loop. Catch this with a pin or needle, and pull it up. Don't cut the threads too short to knot!