Through the website. Find my can brick and erase your phone remotely. It just needs to find a wifi connection (not even connect to it, just register a connection) to do so. The 'find my' location also works with the phone shut down. It uses other apple devices nearby to pinpoint a location.

Online of its an iphone. Or call The carrier. They can do it too.

Samsung is the same

You can not only use any browser, but also any other iOS device. If you open Find My, go to the Me tab and scroll to the bottom there is a “Help a Friend” link there that will open a private browsing session so someone else can login to their iCloud to do all the Find My functions without affecting your device and without you getting their login info.

You should share your geolocation with family or someone you see often . They can do it or we did ours through other devices . Apple Watches do this too .

You can do it through the icloud. You mark it as lost and can add a message for people to read.