Everyone has their own settings. The settings can be found by clicking your image on the top right corner and pressing "user settings". From here you can set your language, view your profile picture and add additional information to your profile. The additional information is visible in your user card and will also help others find you in the search.
From the notifications tab you can set general notification settings, such as enable or disable desktop notifications, enable or disable email notifications and the daily digest.
You can also see all the notification settings per channel and change the ones you want. These channel notification settings can also be managed from within every channel.