If you don't have a real Atari computer or an PC Atari emulator, you'll need to follow these instructions:
Download "Altirra" here (v1.7 or later) this is much simpler to use. (Windows XP/Vista etc) After installing use file boot image and select any game file and you are away!
Download other games 8-bit Atari games from these sites: atarimania , fandal , atarionline.pl and many others. Save them to the same Altirra folder. Tip: For most machine code games make sure you Disable BASIC, for my games you will need to Enable BASIC!
Or download Atari800Win+4.0 and also X-Former from here http://atariarea.krap.pl/PLus/index_us.htm . Then run the Atari800Win+ installer program and unzip X-Former and copy the ROM files to the Atari800win+'s ROM subdirectory. Then use Atai800Win+ (Windows XP) instructions below: