You have to dig in to each extension a little bit to see what formats they offer. For the extensions in the link you provided, it looks like they are PDF only.
In general, there are two ways you can use Quarto extensions:
- You are starting a new Quarto project and want to use the recommended template.
quarto use template ...
- You have an existing Quarto project and want to use a new extension/format.
quarto install extension ...
The first option will create the directory, install the extension, and copy over the template for you to start working on. The second option will simply install the extension in the working directory and it will now be available for you to use.
Hope this is helpful.