how to configure my Mac to allow calls using iphone

Apple has a document Allow phone calls on your iPad, iPod touch, and Mac describing how to make and receive calls on another device (ie. your Mac) and the first task is to set up FaceTime on your Mac. This is the software which will activate when your Mac ultimately receives a call.

Then on your iPhone tell it to send calls to your Mac.

Go to Settings > Phone > Calls on Other Devices.

Here will be listed all your devices signed into the same iCloud account, and you can turn them on with the switch.

Turn on Allow Calls from Other Devices and below that select the device you want to have receive the call.

If you carrier permits Wi-Fi calling you can also turn this on in Settings > Phone > Wi-Fi Calling

See the document Make a call with Wi-Fi Calling which comments that "...you can make or receive a phone call if you have a Wi-Fi connection in an area with little or no cellular coverage."