To start using Easy Templates for Jira issues you will need to install add-on from Atlassian Marketplace.
How to create a Template from Jira issue
How to create a new Jira issue using Template
How to create Jira epic template
How to manage Templates
How to manage Template fields
How to apply a Template
How to copy a Template
How to work with Variables
NOTE: we are holding off distributing of Data Center version of Easy Templates for Jira add-on until the further notice. Our goal for now is to focus on Cloud version experience improvement and supporting Cloud platform evolution.