How to create navigation links to the second application in the project folder?

Question

ASP.NET

Good time.
I have a project with 2 applications. I made friends with each other by creating links.
The question is this:
Please tell me or poke me into how I can make a regular link from the main application to a secondary one?
The first application works as a basis, and in the second model from the application database.
Thanks in advance to everyone for your help... I hope you can help.