Coming from the background of a martial arts class, i'd recommend becoming more involved in the lessons.
After a shared experience like a yoga class, it can be easy to strike up conversation about some techniques you learned, a movement or pose you're having trouble with, or the lesson itself (how the instructor dealt with a topic, the pace of the teaching, etc).
The people who you're sharing the class with are likely to have a lot in common with you about these topics, and they will have just spent an hour with you being physical, so they aren't likely to be uncomfortable talking with you.
To become more involved in the class, you could try some of these suggestions - but it will all come more easily with time.
- Be active in the classes and engage with the system
- Interact with your teacher when appropriate*
- Think actively about the lesson content, try to explain it to someone afterwards in private to deepen your understanding
- Practice in your own time
*This appropriateness may vary according to the discipline - in a martial arts class, I find it only appropriate to comment on something with the instructor if we've been training together for a long time, or if there is a comedic moment in the class - your situation might be a little less relaxed, so perhaps limit your talking to the end of the lesson.