Here is the link to the pattern:
http://www.lionbrand.com/patterns/81046AD.html?noImages=0
It’s a Lion’s Brand yarn pattern, so I hope you already have an account. 
Here’s what I’m wondering…if I need to knit in the round, do I knit back and forth until I have enough stitches to make a round? Or am I supposed to somehow “knit in the round” from the beginning (starting with 3 stitches)?
Thanks for any and all help.
This pattern is not knit in the round at all. You only use the circular needle to accommodate the large number of stitches that you will have before you finish. You work back and forth in rows all the time. You could start on a regular needle and then transfer your stitches to the circular later once you get more stitches if you want, but you can work on 3 stitches on a long circular as well.
Ahhh…thanks for clarifying that. I appreciate it!
there is that common misconception with a lot of people… circular needles do not just work in the round. I do all my knitting either on circs or dpn and do not even own straight needles at all. But this confusion we see all the time.
What I want to say: listen to Jan and feel in good company with your question 