For emulating games, there must be an emulator that is attached to the PC which behaves as a Console and allows games to be played. ROM is the storage system for data used by the console. A number of free console emulators are available online. The PC's configuration is a governing factor for the games being played. For playing games, all it requires is to install and run the emulator software followed by plugging the console into the PC and choosing the files to be loaded. If the console is not compatible with the PC, games can be downloaded online keeping in mind the severity of disposing these files illegally.
The principle of emulating games - in order to play games on your computer, your PC must be equipped with an emulator, a program which acts as a console, thereby allowing you to play games. The data storage system used by a console is commonly called called a ROM (Files that are read by the PC)
Note: it is illegal to dispose of a Rom of a game without owning the original.
Each console has its own emulator, e.g.: with Kega Fusion you can emulate your Sega games, PCSX2 for PlayStation 2 games.
The configuration of your PC is a factor: gameplay will depend on the memory, processor performance and graphics card available.
Play the game console on your PC
Once the emulation program is installed and run, simply plug the console into your PC and choose the type files to load.
If you do not have the console or the ROMS are damaged so that the console is not compatible with your PC, you will find websites offering downloadable games; but be careful because it is illegal to dispose of these types of files.