I think Blogger by default restricts the use of H1 tags to only post titles. I believe this can be changed, so just take a look at the settings and your theme's code. It should be there.
I know very little about "blogger" but h1 tags, i do know about. If you're able to ensure every page has an h1 tag, do that. Make sure your h1 tags (blog, post, page or title) defines exactly what that its about. It should define the entire page, in a few short words - typically 5 words or less.
There is already a h1 tag in the blogger you can change that or modify that. You do not need to create a new h1 tag for this. If you want further details about this then you can take help by watching some video tutorials.