The basics can be picked up in a few hours. Learning the ins-and-outs of the game can take longer, up to several days.
As an alternative to self-study, there are numerous online poker schools that will select a coach and training program for you. But here it is important to assess whether the teacher himself is able to play, and it is not at all easy for a beginner to do this. The wrong concepts, imposed at the very beginning, will delay your poker development for a very long time.