Your Inventory page is where you store all of your belongings. When you create one call it 'Your Name Inventory'. This means that other students, teachers and workers can see the things you have and you can remember what you have bought or possessed.
The most important things you should include in your inventory page is: your wand, your house crest, any badges such as prefect or head girl/boy (if you have earned any), your main school supplies (only the important ones), any certificates you have earned and your pet. (Owl, Cat, Rat/Mouse, Frog/Toad, etc.).
When you have got something new, make sure you add it to you inventory page otherwise other people will not know what you have. For example you may need a certain book for a class and if it is not in you inventory you may not be able to join in.
Remember, though, to be honest of what you have. There is no point in lying and pretending what you have and adding things to your inventory page that you haven't even bought/got. If you do your user will be expelled from Hogwarts permanantley. If it happens again your user will automatically be banned from this wiki.
Here is an exmaple of an Inventory Page: (You can list or show pictures of the things you have got).
9 and 3/4 Wand - Willow, Phoenix Tail
Slytherin House - Badge
The Standard Book of Spells
A History of Magic
A Beginners Guide to Transfiguration
One Thousand Magical Herbs and Fungi
Magical Drafts and Potions
Fantastic Beasts and Where to Find Them
The Dark Forces: A Guide to Protection
Owl - Trix