Applying to a major or minor in Mathematics is a simple process of meeting with an advisor to get registered in the online system. You may want to talk about exactly what your options are, and whether our program fits your interests and needs.
The advisor will be interested in what math courses you have taken already, which major option you are interested in (if you are applying for a math major), what courses you might be planning to take, and perhaps what your career interests might be if this is something you already know.
You should make a point of discussing with the advisor exactly when courses you might want to take are offered; many of our courses are in year-long sequences that begin only in the fall, and a few of our courses are only taught every two years.
After you have discussed at least a rough plan for completing a major (or minor), the advisor will register you as a major (or minor) via the online major-add-system.