Disable Drop Down Menu

I have a site that I am building offline. It is a 3.3.2 version in a Lagada theme.

How do I disable the Drop Down menu for my pages?

I saw on another post that I should post this code into my Css:

“#YourMenuId ul li ul{ display:none;}”

However, I am not sure what “#YourMenuId” is or where to put it.

Thanks,

Raymond