1. How do I cast on when I already am knitting?
You shouldn't be working in the round yet. You should be knitting rows, not rounds
2. Since I knit continental I assume I need to cast on to the left, not right tip (once I figure out how to do it!).
Knitting continental only means that you hold your yarn in your left hand -- you will still be casting on to the right tip of the needle. After you cast on the 8 stitches you will join your piece to work in the round. Use a backwards loop technique to do your cast on -- the video for that cast on is here. Scroll down til you see "Single Cast On.