Um, adding a full stock of cichlids to the tank while doing a fish-in cycle is not a good idea. You want to check your levels of ammonia on a daily basis. If they get up much over .5ppm, you need to do a water change to bring them down (this will happen a lot). Once you start getting the ammonia levels staying down (this may take a while), you need to start checking more for nitrites... if they get up much over .5ppm, you need to do a water change to bring them down. Obviously, you will need test kits for ammonia and nitrites. In a big tank like a 75g, a python water change kit will also be useful.
This process will be much quicker and easier for you and your fish if you can stick something from an established tank in there... like some filter media or a handful of gravel. If you don't have another tank, maybe your fish store will let you have some media. Otherwise, you'll be doing water changes about every other day for a month or more. Live plants in the tank will also help, if you have the hood that came with the tank get low light plants, preferably tough ones because lots of cichlids tear up plants (or you can put them in a net breeder or somewhere where the cichlids can't get at them... they don't really need to be planted. This will also keep them up closer to the light, so they grow faster).
