How To Access A Function In Another Class

So, I am reorganizing a winform application I wrote to make it more readable and maintainable. The previous structure I used had:

1- a login form with some connection objects

2- an import process start form with some import objects

3- a log writer class that receives data from the import process and writes a log file at the end of the import process

The code quickly got too messy, so my goal now is:

1- a login form with only form events

2- an import form with only form events

3- a class with all the functions

Basically, my class with all the functions (3) looks like this:

Public Class MyProgramMainClass
Public Function test()
Dim testing As String = "test"

[Code].....