how do I set up a personal hotspot on my iphone?

By contacting your cellular carrier and asking them for "tethering" service.

Then follow these instructions:--> How to set up a Personal Hotspot on your iPhone or iPad - Apple Support

Regards

Giulio

Whether or not you can set up hotspot on your phone depends on the features that your carrier provides. Some carriers do not provide a hotspot option with their cell service.

Home Screen > Settings > Cellular > Personal Hotspot > On

More info here: How to set up a Personal Hotspot on your iPhone or iPad - Apple Support