3. Click “FaceTime” from the top menu and select “Preferences”
4. If it’s not already selected, click into the dropdown menu next to “Default for calls:” and select “OpenPhone”. If you’ve saved the app under Applications on your Mac, it will appear as “OpenPhone (/Applications/)”
Once you've updated that FaceTime setting, you can go on most websites from your browser and click a number. When you click a telephone number on a website, you'll see an option pop up to dial that number in OpenPhone.
After clicking the pop up, you'll be taken to the OpenPhone desktop app where you can click "Call" to dial that number.