It really depends on the transmitter and firmware. If you haven't purchased a transmitter yet, I recommend the Turnigy 9xr or FrSky Taranis. The Taranis comes with OpenTX and the 9xr can be flawed with OpenTX. The Turnigy 9x can also be flashed once modified with a flash port.
Most transmitters can be programmed using the console and buttons on the front. Cheaper transmitters have to be connected to a computer.
There is a lot of support for the Turnigy transmitters available here and on other sites.