If I have paid for an item how do I fill in the expense to claim the money from the company?

I've got you covered, shelly-booty-bti.

Yes, you'll fill in the details for the item you purchased. I've got steps to help you record the business expense you paid for with personal funds.

Before that, make sure that you have created an equity account: Add an account to your chart of accounts in QuickBooks Online.

Once done, you may now record the expense you paid. Here's how:
 

1. Click + New.
2. Choose Journal entry.
3. On the first line, select the expense account for the purchase.
4. Enter the purchase amount in the Debits column.
5. On the second line, click Partner's equity or Owner's equity.
6. Enter the same purchase amount in the Credits column.
7. Hit Save and close.

Additionally, I've included this article that'll help you on how to record personal money you use to pay bills: Record an owner's contribution or capital investment in your business.

Let me know if you have additional concerns about tracking your expenses in QuickBooks Online. I'm always here to help.