@epoch
are you asking
1) how to save your game in VGBA? or
2) how to access the ".sav" file?

For question#1, you just have to press the menu/title bar and choose "Freeze State". That will create a save file, it's the one that has a ".sav" extension. If you want to continue playing from the save point, load the game, press the title/menu bar and choose "Restore State".

If you are asking question#2, what you have to do is open your "File Manager" and browse to the folder where you placed your GBA file and look for the file with a ".sav" extension. That's it!

And next time, post your question on the message box, not on the subject box.