So for about the first hour or so of the game you won’t be able to access the items. Eventually you will get to a cave with a Sabertooth that attacks you. You can’t beat it yet, but you do escape into the land of Oros. This is the main area of the game and where you will find the stash for your items. After you do the mission where you need to collect green herbs, you can access you reward stash. This is where you can find all you new weapons and skins. The throwable items don’t reset but you can craft them yourself after you get them into your inventory.
This is also where you will get your crafting materials from saving villages and increasing population. These will reset everyday when you sleep and wake up. Anything extra from your pack will also go to the stash, crafting materials you can’t carry anymore. Taking the strong holds and enemy bases will give you different materials in your reward stash each day so be sure to take those down when you come across them.