Content for Newsletter Page

I am having issues creating a channel/collection for my newsletter page please help me

my routes.yaml looks like
post: page.home
template: page

controller: channel
data: page.newsletter
filter: tag:Newsletter

template: index
permalink: /{slug}/

tag: /{slug}/

here is my newsletter page ​​ and my newsletter posts which yes are tagged with Newsletter are not populating also is there any way to add css to the post view that populates like on here

P.S if there is any other way to have all posts tagged with newsletter appear under the page I am all for it.