Add notification menu to your navigation. Read the docs. You have to customize it or get that theme. Its not in current version, get development version for GitHub.

hello, Where I can see the menu item notifications please ?

This is not possible yet. But will be added in near future.

Hi, how did u converted your desired Q&A data into simple linear Q&A database? Thanks

Practically it can be done by doing some changes. But there are not any simple steps for this. You can look in both notification and hook into BP or AnsPress notifications.

As I said a few minutes ago in a question, this will be fixed in 2.4. Currently working on same issue.