Download the solution and import it to CRM. Read here on how to import CRM solutions and how to enter the product key for extended trial version (7 days trial does not require product key) or for paid license.
Add the Security Role: Dynamics Clone User to all users that wish to use the clone function.
The clone function is available in the list view of all system and customized entities, when only one record is selected. The clone function is also available in the forms of Accounts, Contacts, Appointments and Tasks entities.