In order to hide topics or mentions of users that you follow, go to the settings tab. You will find the box in the bottom right corner of the screen. Click on it, and you will see a screen with 2 tabs. You have to click on the "hide topics and users" tab.

There you will find "Who to Follow" and "Tag People" options. The first one will ask you to enter the username of the user you want to hide. And the second one will allow you to enter tags that you want to hide.

Once you do that, you will find yourself in a different page. Here you will see that the list of users and topics you follow is no longer visible. And there you will find a new option "Who to Follow".

The "Who to follow" option is the same as the one you will find on your Twitter account page. You will be able to add new users or to check out your favorites. You will not be able to add tags, but the option "Hide Topics" will be visible.