i was robbed and was iPhone was stolen with my iCloud logged out of the device how do I lock it

This document has a list of things to do if your iPhone, iPad, or iPod touch is lost or stolen. --> If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

- The Find My service described in the article is the only recovery feature Apple offers. It must be set up before the device is lost.

Read this support article to learn what you can do if Find My iPhone or Find My iPad isn't enabled on your missing device --> If Find My iPhone or Find My iPad isn't enabled on your missing device - Apple Support