Does the fan have a battery powered remote that controls lights/ fan separately? If not, look up the model and see if you can order one. If the model is remote capable, you can either use your existing one or pair a new one, and then use a Bond Smart Bridge to mimic that dumb remote's signal and network it into your smart home network. Works great for two ceiling fans in my home.

If your fan model is not remote capable then pull the switch off the wall (after cutting power at your breaker box) and see if there's an unused red wire in there. That's what's usually used to control the fan, while black is for the light. Whoever vaulted the ceiling may have just connected both to the black wire at the fan and not bothered with separate switches on the wall, and hopefully there's an unused red sitting there waiting for you. If it's not there then its a hassle to run one for someone who's inexperienced, so at that point I would just replace the fan with a smart one or use the remote method discussed above.