You need find a frequency that is free in your area (good luck). You need to find a location for the repeater that will cover your intended service area. Then you need to submit it all to one of the FCC's frequency coordinators for review and approval ($). Then they submit it to the FCC for final approval and licensing (more $).
Assuming you don't happen to own a radio tower, you would need to lease space on the tower and associated equipment hut ($$$). If you need to install an antenna and coax, expect to pay about $5-9,000 for that work not including the antenna itself.
You might be better off checking with the area radio shops to see who has a "community repeater" available for your use. Rather than putting up your own, you can lease the use one one that already exists. Usually they have a much wider area coverage than any one you put up yourself will.