To bulk assign a template to your eBay listings, in the library, make your listing selections and click the Bulk Actions button.
The Bulk Actions button will appear towards the top right of your screen once at least one listing is selected.
Choose Listing Actions, and then Assign Template.
In the popup, select the template name and choose Apply Template to apply the template to only those listings selected in the library, or select the link to apply to all xxx listings matching the current search.
If you've selected the link to apply to all xxx listings matching current search, ALL library listings including those not selected, will be edited to add the selected template.