each time get a little bit closer to your goal.
begin by practicing for a short time, maybe for ten to fifteen minutes. in the next session you increase a bit more, then a bit more until you do about one hour per day. daily practice is best but of course you can do regular practice also each second day or in bigger distances.
do not cross your limits and listen to your body! relax in between the postures and remember that yoga is supposed to be fun! whether you do it alone or in a group, enjoy what you are doing! you will feel the difference pretty quickly, it just changes 