Hello there, @Abdul Rehman.

Yes, you just need to setup one QuickBooks Online company. From here, you can add authorized users to enter your backlog data simultaneously.

To add a user, here' how:

1. Go to the Gear Icon (⚙).
2. Click Manage User.
3. Select the Add User button.
4. Choose the user type, then click Next. 
5. Pick the Access rights you want the user to have, then click Next.
6. Enter the user's contact information.
7. Click Save. 

You can check this article for the step-by-step instructions: Add, delete, or change user access.

To learn more about the different type of users you can add to QuickBooks, you can read through these articles:

• What different types of users can I add to my company?
• Learn about user types in QuickBooks Online

Always feel free to click the Reply button if you have other questions. I'm just a few clicks away.