No "view in browser" option for many email campaign templates.

I have only found an option to "view in browser" available in a limited number of templates, and there does not seem to be any way to add this to a blank or custom template. I can't find any option in the templates or styles that would enable this option; some predesigned Squarespace templates seem to simply have it in place when they are released.

Please help!

There's information on this here: https://support.squarespace.com/hc/en-us/articles/360001280588-Getting-started-with-Squarespace-Email-Campaigns