How do I get a coin encapsulated?

I have a Cheerios Sacagawea dollar that I want to get encapsulated/graded. I have never done this before, so I really have no idea what I’m supposed to do. I have gone to a few sites that offer such services, but a lot of them seem to deal mostly with coin dealers and with huge quantities.

Does anyone know what steps to take and/or has anyone done this before?