How do I create a sub-page?

Hey guys!

I would really appreciate your help with this. I’m trying to create a sub-page for my work page (which is my homepage - it features real projects), so when you hover over Work in the navigation bar, it presents a drop-down menu with a single item (links out to a separate page featuring spec work). Here’s an example.

I’ve tried reading previous forum posts and trying the advice there, but I’ve had no luck.

Any help would be massively appreciated!