How to Add Submenue to a menue

Question

I am trying to desing cafeteria Menue please help me to know how to Add Submenue into menue.Like when i click on Burger Menue button it should show 

 

"Chicken Burger"

"Veg Burger"

 

snapshot is added or refference

 

Please let me know what kind of method is used in.

 

Thanks in advance.