Learning to scuba dive and becoming a certified diver is actually pretty easy.
The first thing you need to do is find a dive instructor or dive school, depending on where you live this may be really easy or very difficult. After you find a dive school, you sign up for classes and you have to do several hours (I don't remember exactly how many) of theory and class work.
Once you have completed the theory portion then you are in the water with dive gear. The instructor will take you into a pool first, a few times so you can become accustomed to the water, looking at your gauges, breathing underwater and moving in the water.
After your instructor sees your are comfortable with the equipment you will have some open water dives and then a night dive, maybe not in that order, but you get the point.
All in all.... it may take a month or two, depending on how your instructor schedules your classes to become a certified diver. The classes are usually easy and geared toward the individual learner. In other words the instructor will go as fast or as slow as you need him or her to go for you to understand everything.
When I got certified (years and years ago) it only cost about $200 or $300 for everything, if I remember correctly, but like I said that was many many years ago.
Good luck and have fun!!!