How can I locate my iPhone that has been stolen?

You can’t. Find My is a valuable feature, but you have to turn it on to use it. It cannot be tracked by you using just the IMEI. Law enforcement can track an IMEI and obtain an approximate location by issuing a warrant to your carrier, but they won’t bother for just a stolen phone. That’s more for missing person locating.

you cant. You must have turned off Find My in that case but check

phone stolen or lost

Learn more about how use the Find My App.

Find My - Official Apple Support

Then look at this Apple article and my additional advice below it:

If your iPhone, iPad or iPod touch is lost or stolen – Apple Support (UK)

Tracking lost or stolen phones

The 'Find My' tracking is to help you discover if you left your phone in the office or the restaurant. Lost or Stolen phones are rarely ever seen again. Unless you have your own armed gang you will not want to contact the organised gang that now have your phone. 

Risk mitigation

Get your provider to 

Cancel your SIM.

Send you a replacement SIM on same number.

You can then put the SIM in another iPhone to get the codes you will need.

Phishing warning

Its possible for a thief to obtain your phone number particularly if you did not have a PIN set on the SIM.  So do not respond to texts to sign into your account! They are NOT from Apple. 

Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

Resign to the fact that if you had a passcode set and you do not provide your Apple ID via phishing texts then your data is safe but you may never see the phone again.

Sorry, but the IMEI number will not help. Apple only provides the "Find My" service to help you locate a lost or stolen iPhone. If you did not have an opportunity to enable that BEFORE it was stolen, there is nothing else available to you to track it. Apple does not directly get involved with an iPhone's recovery.

Unfortunately, with Find My not enabled on this phone, it would be accessible to the thief. I strongly suggest that you do the following as soon as possible:

• Change your Apple ID password.
• Contact your cellular provider and report the phone stolen. They should be able to "blacklist" so that it cannot be used for cellular calls.
• Contact your local law enforcement agency and report it stolen.
• If you have set up any credit card information on the phone, contact each of those credit institutions to report those cards as "stolen."

Good luck!

Unfortunately, if Find My was not enabled, the phone cannot be located on a map. The IMEI will not help.

If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support