Assigning command to Cascading Menu

Hello,

 I have customized the Menu bar to add new tab and cascading me.

(Please refer to attached image.)

I am able to assign "Command" to sub-menu. 

On click of "Main menu" I want to call/execute "Command 1".

Is this possible? if yes can somebody please let me know how to achive it?

Warm regards,

Madhavi