I'd like to get the guide to enter invoice payments manually!

Hello, I'm Jenny from Netkiller., Ltd.

Here're some questions.

First, We receive payments outside of QuickBooks, so we have to enter 'Paid' in each invoice if it's paid.

But cannot find the guide about it on Support Q&A and youtube. (https://www.youtube.com/c/quickbooks/videos)

Also, I wonder if I can delete or modify it after entering payments.

Could you let me know the support guide and youtube video to process it? 

Next, I found there're many menus on Quickbook video, which is differernt from ours.

How can we use those menus like 'Sales'? We can see only some menus.

I'm looking forward to your quick reply!

Thank you.