If you link your Steam Account in the Resident Evil NET website you can unlock all costumes and collectables of the game, is very simple.

1) Register a Capcom Account: https://game.capcom.com/residentevil/en/
2) You gonna have to link your Steam Account with the Capcom Account
3) Ones the game is link to Steam. You may wanna check the items you can redeem by playing the game: https://game.capcom.com/residentevil/six/en/windows/gameitems.html

Check the Tab "GameItems" you can unlock items using points for playing the game.

Hope the guides is useful. Remember to like & save.

NOTE: You can only use the EX Skins in Mercenaries, not the main story. Remember check Nexusmods for Mods.