Inventory is a place where you can store your items or equip new items. Without Inventory, you can't store new gear which you've bought from shops or gotten as a prize, and you can't equip new gear. Once you've equipped new gear by saying it in the topic, you can edit your character sheet changing your primary and secondary weapon.
How to use inventory
Using inventory is pretty simple. All you have to do is create a topic with your char's name and list things that you own, you are allowed to edit that list once you get new items or something happens to them.
When you want to equip new gear, simply reply to your own topic saying "Equip primary weapon as... and equip secondary weapon as..." and then you can go to your character sheet and update your weapons. But you are not allowed to equip or reequip gear when you are in a battle.
- Spoiler: Character Info: