The ability to dunk does not come easily to everyone who tries to achieve it.
In fact the taller you are the easier it may be because you are already much closer to the rim, but that does not guarantee that you can dunk.
But, if you have the will to try and you can already jump up and touch the net, there is a really good possibility you can dunk.
Factors such as weakness in the legs will seriously limit your chances.
Think about your body weight, if you have got some extra pounds you need to loose do it, the strength-to-weight ratio plays a factor in this.
If you need to get stronger and you are doing the dead lifts and squats like you should be doing, be careful how you eat because you may get bigger.
Getting bigger is OK because you could have added more muscle, just make sure it is a lean weight.
Set yourself up with a guide that you can follow to help you learn to jump higher, it would be better than just trying different things and hoping you get it right.
Following a guide will help you to be better focused when you have a plan to follow.
Be persistent with your plan, it could take a few months or more for most to really see results.
If you feel like you have reached a sticking point where you just cannot jump higher, take a week off, come back and work on your leg strength and then get right back into your program.
If you want it bad enough you can do it.