Step 1: Make sure you are logged into Facebook.

Step 2: Click this link https://business.facebook.com/settings/owned-domains/ to go to domains which is under "Brand Safety".

Step 3: Click "add".

Step 4: Enter in your domain name without the www or the https.

Step 5: Click on the "meta-tag verification" option then copy the meta tag in step 1 of "here are the basic steps" and add this to the head section of your home page on your website.

If you don't know how to do this, then email the meta tag you copied to your clipboard to the person who manages your website and tell them the following:

"Please add the following code to the head section of the home page of my website."