How to access methods in forms from a test method in a different solution file?

I have two different projects in two separate solution files. One is a test project containing my unit test methods and other is the main project. I know I need to create an instance of the individual GUI form first in order to access the methods in but not sure how to do this.

Also, I have certain variable values which get initiated only when I run the entire original application. These values are used in many of the methods in the main project. Without them I will just get null values and the test method would just fail. Is there any way to get values for those variables without running the application? I tried to place the logic which fetches the value for those variables in my test method and then call the actual method but this still doesn't work. How do I resolve this problem?