How do you run commodore 64 games

This answer is assuming the question is about actually running games on the C64 hardware. If you want to run old C64 games on a new operating system you have to search for Commodore 64 Emulators (for example the Vice Emulator).

The Commodore 64 hardware normally has three different ways in which you can load games into it, cartridges, tapes or disks.
To play a cartridge game you must turn off the computer, plug the cartridge in (back right slot) and turn it on again. The game will instantly start and does not require any loading time. If the screen is blank, try turning the machine off take the cartridge out and re-plug it again before turning on again. Frequently there can be connection problems on some of the pins. Under no circumstance plug or pull out a cartridge when the machine is on. This will break your C64.

To play an original tape game you just make sure that the tape drive is connected to the tape connector (you cant use any tape drive, it must be one that is compatible with the C64), turn on the computer, insert the tape, rewind it and then press and hold SHIFT while pressing RUN/STOP. The screen will ask you to PRESS PLAY ON TAPE which is what you do. The machine then loads the game which can take from a few minutes up to 15 depending on how big the game is. Many games use fast loaders which often show flashing lines as the data is loaded. Frequently there is a loading screen also and a music piece as the game is loading. Depending on the tape loader program some will show an error message by the colour of the lines indicating that you should rewind a bit and retry loading a piece. Read the manual to check this. Many tapes came with two identical recordings of the game, one on each side. So if loading one side fails. Just rewind it on the other side, turn off the computer and repeat the procedure above for the other side. Some tape games feature so called multi loads which means the game is loaded in parts, in those cases the game will instruct you when to press play, rewind, turn tape, etc.

Actually pressing SHIFT and RUN/STOP is just a shortcut for typing in the words LOAD and pressing Enter as well as RUNing it when it is loaded. By default this will try to load the first program on the tape device. You can also write LOAD your self, press Enter, then play. It will load the program or the first part of the program and then display READY. To start it you would then have to type RUN.

If you have an old tape with many pirated games, chances are these were stored using a fast loader. In that case you need to know which fast loader was used and either load this first in the machine or insert the necessary cartridge that was used. If you dont know which it is, you need the expertise of a programmer to decode the contents of the tape to figure out which fast loader to use.

A disk drive is by far the easiest way to run games as you only have to make sure the drive is connected to the serial port, turn on the computer, insert the floppy disk, turn/push the locking handle on the drive and write:

LOAD "*",8

This will load the first program on the disk. If the disk contains many games you can type this:

LOAD "$",8,1

To make it load a menu of the programs on the disk. To see this menu (which is actually a program listing) you only type:

LIST

The menu will show the name of each program and to load a particular one you just write the name where the asterisk (wildcard) is in the LOAD command that I presented first. Actually you dont have to write the full name but only enough to distinguish it from the others on the disk followed by an asterisk. For example if the disk contains the game JUMPMAN you could write this:

LOAD "JUMP*",8

If the display shows READY after this. You have to type RUN (Enter).