Welcome to unicycling! You covered alot in your short intro, much of which is answered here:
Its a long one but there is a whole lot of good information there. Sounds like you need to raise your seat to help you learn the basics. Ideally you want your leg to be almost straight at the bottom of the pedal stroke while you are sitting in the seat. Later, depending on the style of riding you go into you may want it lower. Even for your height a 16" is pretty small, but it may well be enough to get you started. Lots of knowledgeable folks here to help, also loads of info already posted. Hit that search button hard!
Kurt