There are 2 ways on how to add items to a storage system.
1. with Plugin Commands
2. with a Script Call
The first option is for people that are not comfy with coding/writing script calls. I will give you the same example in both methods.
Lets say we want to add the following items to the storage
1. 3x Item with ID 1
2. 1x Weapon with ID 3
3. 2x Armor with ID 4
If we would use the Plugin Commands, it would look like this
and if we would use the Script calls, it would look like this
You don't have to use both methods! Just use the one you are more comfy with, both will achieve the same thing.
I also made a quick update to the plugin (v2.1.0). You can now specify a "Storage Mode", it lets you specify either "Add/Remove", "Add" or "Remove". If you just want to create loot boxes, then you can set the storage mode of that storage to "Remove", so the player can only take out items. That makes more sense for a loot box.