After the tank has cycled, measure the nitrates and do enough of a water change to bring the nitrate level down to an acceptable level (less than ~40ppm, but bare in mind the reading in your tap water).
Unless there has been bits of plants or dirty substrate or something in the tank then it probably isn't worth cleaning the filter at this stage. If/when you do, make sure you rinse them in the old tank water (which you probably already knew).
Also, if there has been a gap between the cycle finishing and you adding fish then keep adding ammonia each day until 24hrs before you get the fish and check the ammonia etc is at zero before going to get them.