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 Edit Listings, then Listing Title.
In the popup, select to Edit this page of listings only or Edit all listings at once and select Next.
If you selected to edit this page of listings only, on the next page you're able to change all titles for the selected listings by adding text to the beginning or end of the existing titles or edit the titles per individual listing.
Please note that eBay limits the characters in titles to 80.
Once you've completed the changes, select Save all modified.
If you've chosen to Edit all listings at once, set your values in the popup and select Edit Listings.