You will find the notifications button in the main menu or in the top right of the screen by clicking on your profile picture.
The one in the top right corner of the screen shows gives you notifications off all projects you are apart of.
The one in the left navigation menu
shows you notifications of the project that you are in.
It is also possible to find project notifications for every member/team of the project by going to that member/team in Settings -> Members.
How to use notifications
The notification system is useful for keeping track of what happens in the buildings and sites you want to keep track of. It tells you if there has been something new - for example, if a new revision of a building is uploaded or if someone has assigned an issue to you.
Settings for notifications are possible to find as a sub-page to Notifications. Here you will find a filter list for what notifications you want to receive. See here