Can some experienced creators help

[MrRipper]

 I've been making this skin for my team for the 450 gasgas, but every time I export the bike and do all the painted stuff; my bike never shows up in game! So, I was wondering if someone could help me with exporting my skin with Gimp, I would much appreciate it. Also, I already watched the Gdub Mx video and tried what he did but wasn't successful.