for bgb game link to work at all, you need a very fast pc (P3, athlon) and <1ms lag (fast LAN, or localhost). it does not work with all games. some games that work are tetris, pokemon, mortal kombat. You can send me email: your system specs, OS, network specs (if applies), the game, and if it does work, or if it does not work. don't ask "when do you support (name of game)", i don't know. on one bgb, you select "listen", on the other you select "connect". it should then show "linked" in the titlebar. there is also an option "remotejoy" so joypad 2 of one bgb controls the other bgb (which does not have keyboard focus, for example).
Go to the settings and enable ‘link cable mode’. In BGB select ‘link cable mode’. Then press A on your second Game Boy and then Start on the other to start link mode. Once that’s done, take one end of the Link Cable and plug it into your computer or laptop (if there’s an Ethernet port). Now take another end of the Link Cable and plug it into your first Game Boy.