Yoga

I'm trying to do yoga: three times a week.  I'd rather walk because I love doing that.  I am realizing that I need to do something more than walking. . .  build up some muscles in order to continue on my journey.
Gary bought me a yoga system at Aldi.  Hmm  How great do you think it is?  There is an exercise ball: good.  There is a mat: fine.  There are both a band and a strap: excellent.  Then, there is the video.  The lady who is demonstrating is very fit and attractive--of course.  She is the yoga expert.  The problems arise in that she is talking, but I am not hearing her.  I am hearing the woman who dubbed over the video.  I can tell because the fit lady's mouth moves, yet I hear nothing.  There are also times when the verbal instructions don't match up with the visual instructions.  "Stand in prayer pose" plays at the same time as "fit lady laying on the ground."  Also, sometimes the video goes very fast--I get two seconds to hold a pose, and other times I lay in child's pose for what seems like an eternity.
I am trying though.  I figure this is a great way for me to learn about yoga, get stronger, hopefully get slimmer, and feel better.  I do wonder though if I'm doing things the right way--after all, how much should I trust this video?
I'll just keep on keeping on. . . and trying to master spinal twist.