As it is likely an OEM keyfob, it would be helpful to know the source/brand. It may indeed require a visit to a dealer. That said, here are a couple of links that may be of assistance:

https://www.keylessentryremotefob.com/Key-Fob-Programming-Instructions-s/1856.htm

https://itstillruns.com/program-key-fob-range-rover-7307259.html