Was it delivered as a .oxt extension? If so, rename it to .oxt and install it with the Tools>Extension manager dialog (Add button).
If all the templates are in a mere zip archive, then copy them to the templates folder. Either in the installation folder (C:\Program Files\OpenOffice.org 3\Basis\share\template) or in the user profile, see:
[Tutorial] The User Profile. Or use the import dialog in the File>Templates>Organize, select a folder and Import (Commands button).
Please add '[Solved]' at the beginning of your
first post title (
edit button) if your issue has been fixed.
LibreOffice 7.0.3 on Xubuntu 20.10 and LibreOffice 7.0 (portable) on Windows 10.