double knitting question
I am brand new to this forum, just found it while I was looking online for some help with my project. I am a relatively new knitter, about 3 years, and only a few projects. But I pick up things pretty fast and have taught myself a lot with books. However, I am stuck. I am working on a sweater for my son, pattern seemed simple enough. I have just been working the back with a striped pattern, knit one row CC, purl one row CC, knit one row MC, Purl one row MC. However, I have come to a part that I am not sure what to do. I have researched, and determined it is probably double knitting, so I need to learn how to do that, but then I also have some questions. Here is what the pattern says:
Keeping in pattern, k 16sts. Join second strand of yarn and bind off next 15 sts, k to end. Working both sides at once, work even in pattern until Back measures 17 inch from begining.
Ok..keeping in pattern? meaning the stripe pattern or knit one row purl next?
Join second strand of Yarn? Do I use the same color yarn? If I do, how do I double knit with the same color yarn, how do I know which yarn goes with front and which with back.
Work in even pattern? Do I knit purl now, or what does this mean. I realize I am basically doing every other sticth, but not sure which to purl and which to knit and how to figure that out.
Any help would be great! Thanks!