Please note that in order to obtain your pre-order bonus of the "Guild Knight Set" layered armor and the "Hope Charm" talisman, you must first go to the Support Desk Palico in a village and select "Claim Content". As long as your pre-order bonus has been installed, it should appear as claimable content under "Add-ons".
Please also note that when claiming this content, it will say "Contains: Talisman: "Hope Charm", but this also contains your "Guild Knight Set" layered armor. Once the add-on is claimed, go to your tent and go to the "Appearance Menu" tab and select "Equipment Appearance". You should see the Layered Armor selection and you should be able to equip the "Guild Knight Set" layered armor from this menu.