Hi, and welcome to the forum!
What you are asking is not that simple because this is not the way that ProcessWire is designed to work. It's not impossible though, and if you have the skills to create a module you can do it. I can't help you a lot with this, but maybe someone who can will jump in the discussion.
What I can do is help you to get started. Here it goes
To make a page appear in the admin navigation, you just have to make sure that it is children of the admin page in the tree. You can do this with any page with any template.
If you want this page to behave and look like the other admin pages, you will have to give it the admin template... go ahead an try it... when you do this, the page will simply say "This page has no Process assigned". This means, you will have to create a process module that does what you want and assign it to the page you created.
If you edit the page and choose from the several processes that already exists, you can see how it works.
The process modules are on the wire/modules/Process folder of your PW install, have a look at some of them to get a feel of how it works.