Go to "Job Templates" in the main menu and add a template.

When it asks which template to copy from, copy from the "Blank Template". This will create a job template with no items in the estimate.

In the template menu, select "Estimate". There should be no items in the list.

Tap "+" to add items. 

Select "From A Job" in the "New Item" menu.

Select the job you want to copy from. This will open the list of the items in that job. 

Now tap on the check box at the left next to each item (or group) that you want copied into the template. 

Once you have selected all of the items you want copied, tap "Copy Items". This will copy all of the selected items in the job into the template.