Template can be used to apply to a single firewall, or a group of firewalls. A new template is a default template. It has default values. Any changes in the template are considered new values, and when applying the template, only new values will be pushed to the firewall.
Here is an example, an address object is created in a new template and applied to a firewall:
Step 1: go to NSM Manager View/Templates, click on “Add Template”:

Step 2: a default template will show up:

Step 3: Go to OBJECT/Address/, click on "Add" to add the address object "Quad one":

Step 4. Click on “Save”, then click “Close”. Now this template is complete. Click “Done” at upper right corner;
Step 5. This template is ready to be applied. Click three dots “…” under “Action”:

Step 6. Select the group or device, click on “APPLY”:

Step 7. Notice the Apply status is Success. Click “Close” to close the popup:

Step 8. Click “Commit & Deploy”:

Step 9. Select the device, click “Next”:

Step 10. Schedule a time or “Now”, click “Next”:

Step 11. In Summary page, click on “Deploy Now”:

Step 12. Deploy success:

Checking firewall, address object has been pushed over:

Note 1: before applying template to a group/device, the device needs to be added to a group:

Note 2: if the template has been applied to a group/device already, some changes has been made, you want to apply it again, make sure “Apply All Config” is enabled. During application, some warning messages will show, since some of changes have already been made:

Note 3: currently existing settings cannot be modified then apply. For example, address object “Quad one” has been applied. You cannot modify the name, or the IP address, then apply the changes. You have to delete it, apply, and create a new one, apply.