It's a rather a complicated subject for this board. 1) You need to research fish that have similar needs as far as temperature, pH, hardness, lighting, etc. and 2) You also have to choose fish that are not agressive towards each other. There are some books & online resources... but I would suggest going directly to Pet Lovers'. Their fish guy is very good and he can show you specific fish that work well together in a community tank. He can also order fish for you.
Community fish is a category of fish that live harmoniously together.
Thanks! Your answer is awaiting moderation.