How to enter bill - the plan page comes up instead. How do I move forward?

You can enter a bill by going to the + New button, aimy.
 

It appears your current QuickBooks Online (QBO) plan doesn’t include this feature, which is prompting an upgrade. Entering bills is available in the Essentials, Plus, and Advanced plans. 

To proceed, you’ll need to upgrade your subscription to a plan that includes this feature.

Once done, here’s how you can enter a bill:
 

1. Go to + New button.
2. Select Bill.
   
3. Choose a Supplier from the Supplier dropdown.
4. Fill out the necessary details.
5. Hit Save and Close.

For more info, check out this article: Enter and manage bills and bill payments in QuickBooks Online.
 

Don’t hesitate to reach out if you have any questions. We’re here to help.