Check out the sticky post at the top of this forum and read books. Start with "Opening Up" and the podcast "Multiamory" Episode 1.
Read, learn, and read some more and prepare to change your mind, rework boundaries and desires as time goes on, because as you learn more, what you think will change and what you think you want will change.
There are 100 ways to do poly... or as some would say, as many ways as there are individuals. Nobody is exactly the same. But you need to know what you want and what you don't want. Not having a great understanding of that, and the ability to change your mind can lead you into a situation that leaves a bad impression.
If you follow someone into something you aren't comfortable with for the sake of being poly, you will be very disappointed. Knowing who you are and what you want can help you weed through the relationships/people you don't want.