Premiere PRO can easily handle the editing of two cameras or many more and really your question as to whether to get a second camera depends on creatively what you want to do. If you are shooting someone speaking or playing a piano, having two cameras gives the ability to have one possibly shooting the person from the front, and then the second may be being farther way from the side going simultaneously. That way when you are editing you can switch between the shots from each camera angle to give some style.
To edit it is simple. Import your footage from each camera and then drop the footage from one camera into one timeline and then drag and drop the footage of the second camera into the other timeline. Whatever is in the top layer or timeline is going to be what you see, so if you want something in the lower timeline to show you will have to make sure nothing is above it. This is a very simple approach to get you going.
I'm assuming that you do not have much equipment from your question and you are just starting out. So the next step you will need to do is to synch up the sound on your clips from one camera with the other as best you can. But if you are going to be doing a lot of this, you want to do some homework and study up as you will want to have your cameras synched up with timecode and you will want to be shooting with this in mind and investing a few bucks is well worth the cost.