To activate phone capability go to Settings > Connect.
Check boxes to enable SMS and Phone usage. Enter your organisation name under 'SMS From' as per image below.
Rent a phone by clicking on '+RENT NEW PHONE' button. To get a local number select an option in 'Starts with' dropdown.
Click on 'Search' button and select one of the numbers that appear. Click on 'Rent Phone' button, as per image below.
Once phone is rented, add team members who can use the phone number.
To make a phone call or send a SMS, click on contact phone number in Deals or Contacts and select a dropdown option (make a call or send a SMS).
For more details, have a look at this video tutorial.