Here is an example:
The unlocked items can be found in the game menu. Simply open it and select the Rider tab. In the following menu you will be able to select the unlocked items from new items.
If you redeemed a key for the Freestyle Crystalline Pack, you will be able to find the items of the pack in the customisation menu. This is a screenshot of the jacket:
Some items are only available for male or female characters. For example, you will only be able to equip the Freestyle Crystalline Pack content with a female character. The content of the Freeride Woodcutter Pack can only be used for male characters.
Some ULCs will provide content that you will be able to see in the customisation menu but that will be locked until you fulfill certain in-game conditions.
Once you fulfill the conditions, you will be able to equip the item:
Other items will be added to the game by redeeming a ULC key but need to be purchased before they can be equipped: