Making menu button a with gallery sub menu

Hi there,

I have recently started creating my site hnphotographic.co.uk. I am trying to make the portfolio button on my page not clickable but rather have drop down galleries.

Basically I currently have a page titled portfolio and this is in my menu section. I then have two galleries called Travel and Motorsport as sub galleries. What I would like to do is just have the portfolio button not clickable but when hovered over with the mouse the galleries beneath appear and can then be selected. I think I understand how to do this with other pages with page attributes but is it possible with galleries as I can’t find any attribute options.

Thanks for any help!