In Apex Legends, the players can unlock free skins for PS4, Xbox, and PC (Origin). Unfortunately, you cannot use PS4 codes on your Origin account and vice versa, as Apex Legends does not contain a crossplay feature.
Free skins for PlayStation 4
To get free skins for Apex Legends on PS4, you need to have a PlayStation Plus subscription. To get free skins, log to the shop, input Apex Legends, and activate "Apex Legends PlayStation Plus Play Pack".
Free skins for PC and Xbox
To unlock free skins for Apex Legends on PC, you need to have EA Access or Origin Access subscription. Then, you need to log into Apex Legends using an account with EA Access or Origin Access subscription before 30 June, 2019. If you want to unlock free skins on Xbox, you need to log into the game from an Xbox Live account with an EA Access subscription.