Alerts Dropdown

[Wolf]

I've tried many methods doing this but never seem to get it to work nor know how it's done I'm sure it's php coding? :/
Sorry I suck at when it comes to php.

I've seen multiple forums using this alert,
https://community.mybb.com/thread-171301.html
Now I'm trying to basically make a dropdown so when you click alerts theres a dropdown like this..https://i.imgur.com/AgKNzzi.png so then when you click alerts again it closes.

If anybody could help me out I'd appreciate it.