PLS HELP i can`t add repaints to aircraft! :(

I watched all the videos for repainting. I tried around 20 repaints and i did every single step that the people from the videos said. But still the aircraft with the new livery which i installed just doesn`t show up.
Do you have any ideas what should i do? Pls help me

You may be doing it right.
Check the box "show all variations".
It's where you choose the aircraft you want to fly in the Sim.
Sometimes an aircraft isn't listed under what you think it should be.