Yoga encompasses even MORE than this!!! This is just a super simplified outline, and only one style for looking at it. There are many, many more "types" of yoga than just ashtanga.

If you want a physical practice, I suggest you get a DVD or watch a youtube video and practice at home!
If you want relaxation, I suggest you try meditation - just sit down for 5-10 minutes and focus on your breath. When your thoughts start to wander, bring your mind back to the breath - no judgment!

That's a quick way to get into it, but wait - there's more! Awhile back I wrote a little guide for getting started:
https://steemit.com/yoga/@saramiller/yoga-2-0-where-to-start