I follow #nostr.
If you click on it, then all posts with it will appear. And in some clients (#amethyst for example) you have the option to follow the # right on the top of the search.
Discussion
Ok I got what hashtags are! Whats a client? Like in the case of #amethyst?
Yes, amethyst is a client for android. If you want to use nostr from the computer, you can try for example coracle (nostrapps.com/coracle)
There are also clients for apple.
To use a client you'll need your nsec. You should never tell your nsec. To avoid inserting your nsec everywhere, they have also created signers, like Amber (nostrapps.com/amber) for android and nos2x (nostrapps.com/nos2x) as an extension on your computer.
Ideally, you should never insert your nsec in a client, only in signers.