Monsta1973

Hello All I am a complete beginner on here, if someone can show me how to start, i want to download an emulator onto my laptop to play Sega, Atari, Amiga old titles possibly some more but just need some general help in downloading and getting the system up and running. If it too complex then i may have to leave it, but i think i should be ok. Do you pay for the downloads per game etc... or is there a set monthly cost , all help is really appreicated. Thanks in advance.