I don't understand, how do we get that GUI to appear? All I see is a DLL file and I've already injected it.
Firstly, find your Maplestory directory (usually C:/Nexon/Maplestory) then make a shortcut to "GameLauncher.exe" on your desktop.
Google "Winject" and download it (sorry I cant post a link, its considered advertising and I'd get banned). You may need to disable your anti-virus because most AV's see Winject (and most other injectors and dll's) as false positives. Place Winject.exe on your desktop.
Run the shortcut you made to GameLauncher.exe, the Maplestory Launcher should open (dont start just yet). Run Winject.exe as an Admin (or else it wont work).
Select the GG2 dll file (wherever you have it) as the dll in Winject, and select MapleStory.exe as the process in Winject.
Click inject, it should pop up with the trainer.
Click start on the Maplestory Launcher.
P.S. If the trainer still doesn't show up you need to google and download:
Microsoft .NET Framework 4
Microsoft Visual C++ 2010 Redistributable Package
Remember to download them for your operating system (x32) or (x64)
Noob question here. Where the fck is the gamelauncher.exe I only have the setup.exe, patcher.exe and Maplestory.exe please help (Its not in C:/Nexon/Maplestory). I downloaded my Maplestory files from the Nexon EU, so it should be there.