I'm glad to help you with that, support-sweetsav. 
 
In the QuickBooks app, there's no option to add a user. However, if you want to add a user for them to upload a receipt, you can add it through a web browser or your QuickBooks Online account. Here's how:
 
 - Click the Gear icon ⚙ and select Manage users.
- On the Users tab, press Add user.
- Select the Roles ▼ dropdown, then choose the role you want to assign to the user.
- Select the Account management settings you want to manage (only if applicable).
- Hit Send invitation.
 
New users will receive an invite to join the company. Let them select the Let's go! link in the email for them to create a new Intuit Account or sign in if they already have one.
 
On the other hand, if you wanted to add a co-owner as a partner to your company. I've added an article with detailed steps to create a co-owner profile.
 
In addition, you can check this article for you to learn how to add a vendor in QBO: Add a vendor in QuickBooks Online.
 
Comment down below if you have further questions on adding a co-owner. I'll be right here to help.