There are two ways you can rename a template in the template itseld.
In the top left hand corner you can rename here by clicking the name and finding this box
2. Alternatively, you can go to the Settings cog in the top right hand corner > Template Settings > Template Info > Template Name
Here you can give it a description, choose which team(s) should have access to use it and more under 'Owner & Permissions' (lock the template from editing, manage editors etc).