Danny...
In the east, licenses are often required. Here in the wild west, there are no such restrictions to the best of my knowledge. But, Trevor is right. You have to get involved in a railroad preservation project, and prove to the elders that you are genuinely interested in the work.
A locomotive engineer, on the C&TS RR and the D&S line, came to Chama as a snot-nosed youth in 1971. He worked his butt off, at menial tasks, for several years. He worked as a brakeman on the trains, and shoveled coal in the locomotives when we couldn't find someone better qualified. (On the trip from Chama to Cumbres, the fireman shovels some two tons of coal.)
My suggestion is that you persue your education vigorously, and keep your interest in steam railroading as an avocation. Believe it or not, running a steam locomotive is not particularly fun or interesting.
Bob Keller