Find a beginner class, the instructor will be going into more detail as to how to do a position. Also keep in mind that some more advanced people in class may

Find a beginner class, the instructor will be going into more detail as to how to do a position. Also keep in mind that some more advanced people in class may be doing a different, but related pose that gives them a stretch that the basic pose no longer does. What matters is that you are feeling a stretch (and not a painful one) in roughly the place the instructor says you are; if you're not, then speak up and ask about it!