there are a few ways, so we will focus on one at a time 
Number Une: from the website
first, go to: http://vba.ngemu.com/downloads.shtml
scroll down to Version 1.7.1
download the Linux one to /home/user in /home/user, make a folder called VBA, or anything you want, but keep it short, yet sweet.
extract the: VisualBoyAdvance-1.7.1-SDL-linux-glibc22.tar.gz to the VBA folder (right click, extract all)
inside, rename the VisualBoyAdvance file to VBA
make a folder in /home/user called games, and inside games, make on called VBA (/home/user/games/roms is mine)
now, get a game! save to /home/user/games/VBA (or, what you called it)
now, Ctrl + Alt + T to open Terminal (on easy mode, for advance, go launch > application > system > console)
now type (or Ctrl + c, then in console, type shift (^) and Ins)
/home/user/VBA/VBA /home/user/games/roms/fireemblem.gba
rom name (don't forget .gba)
/roms/ = what the folder the game is in is called
and you should be on!
if you go to VisualBoyAdvance.cfg in the VBA folder, you can change the configuration smile
Number Deux: Via synaptic
open terminal (as above) and type: sudo kwrite /etc/apt/sources.list
copy and paste the code below under the asus ones, or anywhere really!: deb http://ftp.de.debian.org/debian etch main
now save, and quit. you may now do one of three things: open synaptic (sudo synaptic in console, or terminal), find visualboyadvance, and click to install
open aptitude (sudo aptitude i think) and do it on there (sorry, not sure how sad)
or, in a console/terminal, type: sudo apt-get update sudo apt-get install visualboyadvance
How to run it: vba then path to rom, so, in terminal:
vba /home/user/games/roms/fireemblem.gba again, the 'roms' folder and game name is different for you
or, if you want to, type:
gvba into a terminal and it will launch. I dont use this, as i think it is slow, but there you go
hope this helped, and you installed VBA correctly
