Hello there, gabibey.
To access and add transactions in QuickBooks Online, you will need to have an internet connection. The required internet connection speed is 3 Mbps or higher.
You'll want to check our system requirements for more details here: System requirements for QuickBooks Online.
I'm also adding this article on how to add an expense: Enter, edit, or delete expenses in QuickBooks Online.
Please feel free to reach out to me if you need more help with QuickBooks. Take care and stay safe.