How to use Load/Save?

I don't understand the way the load/save function works in the radial menu?
I customized my Gavril car, adding a hitch and custom light, then pressed "Save vehicle" in the radial menu. After that, I was unable to reload it. Pressing the "Load" button in the radial menu has no effect...
Any idea?

Thanks.

 

that is to save the damage
--- Post updated ---
the way you do it is go on to vehicle selector and click set as default

 

If you want to save configs you go to vehicle config and select the save and load tab, there you give your config a name and hit save. The game will take a screenshot of your config (place the camera nicely ) and you can select it from vehicles.

 

He shouldn't forget to check the "show custom configurations in vehicles selector" checkbox in the options

 

Thank you Guys, what you have explained here works perfectly, now I can do what I wanted to.
Nevertheless, I still don't understand the use of Load/save in the radial menu...

 

It saves the damage of the car. If you crash your car and click at save button, then recover your car, you can bring back the damage of your car by clicking at load button