Yes, you can use just one premium OpenCart template for multiple domains. Follow the next steps:
Step 1. Set up an OpenCart theme as your main website.
Step 2. Make sure all your domains (your stores) have your hosting provider’s name servers.
Step 3. Follow the Cpanel for mainshop.com (your main OpenCart installation). Create an add on the domain for each site you want to have as your multishop. E.g. shop1.com, shop2.com, etc. When you create the addon domain name (shop1.com and so on) the document root will be filled in like public_html/mainshop.com. Delete /mainshop.com to leave public_html.
Step 4. Go to the admin panel on mainshop.com and add a new store with address http://shop1.com/ (shop2.com/ and so on).
Step 5. That's it, we finished. Check your new shop on shop1.com, shop2.com, etc. Now you will see them without a logo, slider, products, etc. So now it’s time to customize it and fulfill with these items.