Joining/ sewing parts together

ok, i just finished the simple beginners toddler shaw and then sewed the 2 pieces together. the problem is that i dont think i know how to sew them together and this entirely ruined it.
can someone tell me how to join or sew pieces together? you do it with yarn instead of thread right. sorry, but im a dunce when it comes to this.
but i love the videos! they are great! i always play them when i do something new!

Finding the right way to put things together makes all the difference! I think that learning good finishing techniques got me re-hooked on knitting after not doing it for years. I never liked the finished product.

Look at the video for Mattress Stitch. It is a wonderful thing to know because it works for almost everything and is virtually invisible.