What does "Give us a bell" mean?
It means give me a phone call. In this informal expression, us often means me, and bell refers to the sound of a ringing phone.
The saying in a sentence
The saying
Give us a bell
Example
Give us a bell when you land.
When you use it
Use it with friends or family when you want them to call, perhaps after a flight or when they have a moment to chat.
When you do not
Avoid it if you specifically want a text or email. In formal messages, please call me is clearer.