Army ROTC
Navy ROTC
Navy Marine Corps Option ROTC
Air Force ROTC
Coast Guard does not have ROTC
There are scholarships that can be applied for in each of these programs. The scholarship application is different for each of these programs.
Google each of the above, you will find an enormous amont of information for each.
You can also look at Senior Military Colleges, they provide ROTC programs for each service as well.
Other then SMC's, a ROTC cadet enrolls in a public or private university that has a ROTC program for the service they are interested in. ROTC classes are part of their standard curriculum. ROTC is added to the cadets normal college experience.
Read up on all the programs and feel free to ask specific questions once you have a good overview of each system.