There is a float mechanism inside the tank that can be adjusted to allow more water in it. However, if it's a low-flush toilet, what you see as a small puddle may be all you'll get even at the MAXIMUM adjustment.
I suggest this. If you have another toilet that made by the same mfgr, and its water level is to you liking, inspect the 'insides' to see how it compares to the one that has the small puddle. (The mfgr's name is usually found on the underside of the tank's lid.) You may have to visit the homes of a few friends to find one that's like yours but that's all I can suggest. Once you DO make the 'find', adjust the float. When you get to that point, post up again with what you know about the toilet and the float and we'll see what we can do. If you want to hit a book store, go ahead and buy a book on General Plumbing to see if you're up to doing it yourself. It's a lot less expensive than calling a plumber. Just make sure the book has this 'job' described in it.