How do i use skin items ?

[Kurumento]

So basically, im looking everywhere but i can't find by myself where i unlock skins by using skin loot. Its from my class so i should be able to use them...

[z00t]

Any skins in your backpack need to be activated / unlocked, by clicking on them. Otherwise you are just carrying them around.
Any character can unlock skins for any of the other characters. Any vehicle skins you find will be available for all your characters.

When you are in Liar's Berg there is a quick change machine there. Change your cosmetics, name and respec your skill points at these.
There is a quick change in Sanctuary as well.

[Kurumento]

The inventory you are talking about is the same inventory i find my weapons, shield, etc ?
If yes, then i am not able to find them in any of the category, or maybe i am really just blind.

[z00t]

You do start the game with several heads / skins unlocked already.
Your backpack is where you will find any skins you have picked up or earned. It will not show you any that have been unlocked.
The backpack (inventory) can be sorted to show weapons only and other items in groups. Click on the top of the display to see how the sorting changes.
You need to go to a quick change machine to see different skins etc.

[Draekus]

here's what an unlocked Skin looks like :
https://steamcommunity.com/sharedfiles/filedetails/?id=1987017713
notice that there's no level requirement.

here's an unlocked Head :
https://steamcommunity.com/sharedfiles/filedetails/?id=1986689245

and here's a guide about where to find some :

https://segmentnext.com/2012/09/19/borderlands-2-skins-and-heads-unlock-guide-how-to-customize-your-character/

[Kurumento]

Oooooh thank you very much ! Finally some space is made in that inventory !

Have a good day !