Download winuae and install, either purchase Cloantes Amiga forever or search (google) for an Amiga kickstart rom, usually v1.3/v3.1 is enough, put these in your roms folder, put your amiga adf files in a game folder, find and load your adf(game)file and try one of the default configs, amiga 500 or amiga 1200, depending on the game, if a demo/intro appears, try pressing F1, Enter, Space or mouse/joypad fire, the game will load (hopefully) and away you go.
for more info, read forums etc..
hope it helps, if you get stuck post back with your problem.
http://www.winuae.net/