You will apply for a Montana Security Guard License with an application:
Private Security Guard Application
The steps to becoming a Security Guard in Montana is similar to a lot of other states: you need to meet basic requirements such as age, language proficiency, and other usual security licensing requirements of this nature.
Furthermore, to get a Security Guard license in Montana, you need to take a government approved MT Security Guard licensing course:
Your Montana security employer will administer this course.
In Montana, the government body that controls a MT Security Guard's license is called Montana Board of Private Security. So, it is The Board that will have to approve your MT Security Guard licensing course.