@Gestour ok i will figure it out thanks for the help

I don't have an Android device, so I can't tell you where it is. It should be there with your aircraft designs folder that you use to XML.

@PvtSAD

@Gestour im sorry, i cant find that folder

You need to move the file into your simpleplanes mods folder, and then when you open the game, there will be a new Mods section. You activate the mod there.
@PvtSAD

@Gestour how does one do that because i downloaded one but i didnt know what to do from there....

You can use mods.
You cannot create mods.

@Jasperjl android

It depends. Do you have android or ios?