Problem with creating a login form

Question

Hello

I need guidance in creating a login form.

I have the main form, where the main GUI is.
I tried creating a new form and calling it from the main form but with a condition.
When the password and username are true, then the main form gets initialized, simple.

The problem is about getting the login form textbox data to main form.
How do you do it? Or should I do the login some other way? Call both forms from somwhere else?

I've read that C# doesn't have popup with textbox. I found that I could use VB for that, but I couldn't get it to work.

Thank you