I'm thinking that Gameboid must create an app folder and in their must be a game/Rom folder that's where I'm assuming you place the downloaded roms so Gameboid can see them.
1) does it keep asking you for a bios.bin?
2) the best thing ive done is to create a folder in my memory card called GBA games and place my bios and my game roms in that folder. DO NOT extract the .zip file
3) when I open the GBA I scroll through the Game folder to which game i want and just touch it and it starts
4) romhustler.net has some of the best free roms that ive found.