Some people and patterns will call it casting off, but you may be more familiar with the term "binding off." I assume you've made at least one project (or thirty...) before starting a sweater, so binding off shouldn't present too much trouble. Here (Continental/English) is a helpful video on the most basic BO method, to refresh your memory.
The asterisk means you repeat from the occurrence of the symbol. So, BO 3, k3, BO 3, k3, etc. until you run out of stitches.
Then take one of your size 2 needles in your right hand, knit all your stitches, and then continue on with both 2s, thus transferring your work to size 2 needles.