No$GBA, pronounced "No cash Gameboy," is a Gameboy Advanced emulator that allows you to emulate GBA games on your PC or Mac. Among the games available for this emulator are the Pokemon series. The original releases of these games allowed players to link up their Gameboys and trade monsters over a local connection. Although you cannot connect to another player's game directly with No$GBA, it does allow you to open up a second game image and trade virtually using a single computer.
Open the No$GBA program on your computer. Check for updates to ensure you have the most recent version running on your operating system. Download the ROMs for the Pokemon games you want to link together. Make sure the versions of the games you download are compatible with the game link (Red and Blue versions, Silver and Gold versions, etc.). Two games that are not compatible with each other over a physical GBA link cannot be linked together with the No$GBA emulator.
Go to "File" and click on "Game Cartridge 1." Choose "Browse" when prompted to enter the game's directory, find the first Pokemon game and click "Open." Pause the game.
Click "File" and choose "Game Cartridge 2." Start the second Pokemon game by clicking the "Browse" button, finding the game file and clicking "Open." The second Pokemon game will pop up in a new window. Click "File" on either No$GBA screen and choose the "Link Games" option. Continue as if you had two Gameboy consoles connected with a physical link.
Downloading ROMs is intended for individuals who already own a physical copy of the game and is illegal otherwise. Do not download any emulator files if you are not in possession of an original copy.