Under Voice Application(In order to setup Twilio and find the required keys check this article)
After successfully connecting the Twilio number, you will be able to make phone calls either by clicking on the number of the contact in the All Contacts view:
Note that you can edit the number here on the fly:
Or you can call the contact from the lead’s profile:
When you make the call, you will see all the data, and you will be able to add notes during the call:
You can also choose to record the call or not. And once the call is done, you can re-call the contact from the same window:
You can see all the call logs inside the lead profile, as well as edit and/or delete notes, or even add new ones:
Moreover, you can listen to the recording (you can adjust the playback speed) and you can download the recording if you would like to.