Ok, for this, I'm gonna assume that you know how to use an Acekard and micro sd and all that basic stuff.
Here is what you are gonna need:
Acekard (or any other flashcart, however, i'm using my Acekard 2i)
Micro SD
Real GBA game
A .sav file of the save file you want to use. Note: If you have a gba save file that's not a .sav file, go here:
http://gbatemp.net/index.php?showtopic=153434
GBA Backup Tool 0.21
Here is the link:
http://filetrip.net/f3228-GBA-Backup-Tool-0-21.html
Download the GBA Backup Tool 0.21 and put all the files that come with it inside your AceKard. I put mine in a folder named GBA to make things more organized for me, but that is not necessary.
Put the real gba game inside the slot-2
Turn on DS and go to the Acekard and select the Gba backup tool folder. Then go to the file that's named "GBA Backup Tool Version 0.21 By Rudolph" and open it.
Press A on the first option. At this point it MAY freeze. That is normal, it's just creating another folder in the SD card. Just restart the DS if that happens, don't worry about what it says on the top screen for now, just restart it as soon as it freezes, or wait 10 minutes or 100 minutes, it won't matter. Just turn it off when you see it happen.
Now turn on the DS and go to "GBA Backup Tool Version 0.21 By Rudolph" again. Press A to get to the menu. Now press B which is "New SAV file create" then press A to confirm it. At this point, a little meter should come up for like a split second then the thing should freeze again, that's normal. Just turn off the DS and don't worry about what it says on the top screen. Just like before, it doesn't matter if you wait or not so save yourself some time and turn it off when you see it freeze. Then take the SD card out of the Acekard and put it in your computer.
Go to the SD card and find the folder that says "GBA_Backup"