how do you unsilence your phone?

There are several possibilities depending on the circumstances.

The ring/silent switch on the left side of the phone. How to put your iPhone on vibrate, ring, or silent mode - Apple Support

or Settings > Phone > Silence Unknown Callers. Detect and block spam phone calls - Apple Support

or Do Not Disturb. Use Do Not Disturb on your iPhone, iPad, and iPod touch - Apple Support

Neither one of those options is applicable if Do Not Disturb is not on.

It would be better wording if the "Silence" heading said "When Do Not Disturb is on, silence:" Always or When Phone is Locked.