Go to "Processes" tab (1). Click on menu (2) button and select "New Template" item (3):

Process template creation wizard will be shown in popup (4). Populate Process template name (mandatory field), description (optional),  select manager if needed, and specify process admin(s) (by default current user will be set automatically):

Click "Next" button (5) to show next step of wizard (6). Select data source object (7) and check checkbox (8) if you want future process based on this template to be allowed to start only once:

Click "Next" to go to the following wizard step (9). Select method to start the process (10) and check "Allow duplicates between versions" checkbox (11) if needed:

Set up notifications at the next wizard step (12):

At the last wizard step (13) you can review your data and save the template:

The process template builder will be opened. You can edit settings (these settings will be applied to processes based on this template) - click the proper menu item (14) to go to the settings popup (15):

Click "Lock" (16) menu item if needed (only users with System Admin privileges will be able to edit this process template).

On the Processes Tab column "Is Template" (16) shows templates:

User can create new process from process template.

Go to "Processes" tab. Open menu and select "New Process From Template" (17):

In the popup opened (18) populate "Process name" (mandatory field) and select available template  in picklist (19):

Click on "Save" button and Process details page of new process will be opened.