Go to Calendly.com to obtain your Calendly link.

Copy your the text after calendly.com/
 
 

Go into the editor of your PreciseFP template that you wish to add Calendly to.  (Templates > My Templates > Click on your template > Click on the Customize button

Locate any empty cell.  It will have a + icon if it's empty.  Please view this tutorial on how to add new fields in a template.

Click in the empty cell then click on the + icon.
 

Click on New Element
 

Choose Calendly from the Graphical elements
 

Paste in the text from Calendly and then click on Create.