Where do you go to restart the phone?

See these two support articles:--> Restart your iPhone, iPad, or iPod touch – Apple Support, and/or:--> Force restart iPhone – Apple Support

As far as your "what to do after?" question, please specify your needs/issues.

Regards

Giulio

Just a reboot?Press the power button and volume up at the same time then slide power off on your screen. To turn it back on, press the power button until the apple logo appears.

Nothing will happen after a restart/reboot. It is just simply setting the phone on and off