@elkaki You can only upvote with Mastodon (with the star), not downvote. With Friendica and Hubzilla you can also downvote (but I've never done this, only as a test).
You would have to copy the URL of the magazine/community into the search field on Mastodon, then you can follow it, etc. It also works with all other URLs (also posts) from the ActivityPub-Fediverse (also Peertube videos and channels that you find via #sepiaserach for example).
@feditips @ernest