It'll be specific to your device...consult the manual. Also, not all phones have hotspot functionality built-in. My last two Samsung Galaxy phones (S3/S6) both have the feature.
Another (better) option is to use a dedicated data "mifi" hotspot, but that costs extra. I found that my phones eat batteries pretty quickly with the phone, where my Verizon Jetpack mifi will go 6-8 hours on its own battery.
Bob (W6KD) Colorado Springs, CO D*STAR Hangouts: XRF555A (persistently linked to XRF002A) XRF720C (Colorado Front Range reflector)
I was able to tether my android phone to Pi-Star with no problem. A couple of buddies were also able to tether their iphones using the same procedure. i have a writeup explaining how to modify the Pi-Star system to allow the USB tether. Pi-Star may have been modified by this time to allow tethering without my mod.