In order to use your Mac for phone calls, you will need to sign in to both iCloud and FaceTime with the same Apple ID on both your Mac and iPhone. And both devices will need to be connected to the same network. A Bluetooth connection is not needed.
On your iPhone, go to Settings > Phone > Calls on Other Devices, then turn on Allow Calls on Other Devices.
On your Mac, open the FaceTime app and go to FaceTime > Preferences and check the box for Calls From iPhone.
After setting it up to share calls between your iPhone and Mac, you’ll see a notification in the top right corner of your desktop when you receive a phone call. Click the Accept button to answer the call.
From the Contacts app, select a contact and click the call button. From the FaceTime app, you can do the same thing by clicking the telephone icon to make a voice call (instead of the video-camera icon to make a FaceTime call). Also from the FaceTime app, you can simply enter a phone number in the search box and then click the telephone icon to place a call, which you can’t do from the Contacts app.
You can also dial a phone number directly from Safari on your Mac as well.