The Click-to-Call panel will display after the InsideSales call center is implemented.
The Click-to-Call tools interact with all of the main Salesforce object types (leads, accounts, contacts, opportunities, cases). In order for the Click-to-Call tools to appear in the "sidebar" area for each object, we need to implement the InsideSales Call Center. Once enabled, the new InsideSales Call Center (based on Salesforce Open CTI) will automatically add Click-to-Call to the sidebar.
To implement the new Call Center:
Enable the Call Center
Click Settings > Customize > Call Center > Call Centers.
You may see a page introducing you to the new Call Centers.
Click Edit on the InsideSales.com | Click-to-Call Call Center.
Under Call Center Users click Manage Call Center Users, then Add More Users.
You can filter your results, otherwise just click Find to find and add all users.
Select the appropriate users and click Add to Call Center.