This is a lot of work over several files. Start looking at the files in the skin folder, and it will become clear what to do.
When you have researched these files and start working, I can help further with specific questions.
I believe that when DFX 5 comes out it will have 3 menu pages, so you might want to wait.
I created a 3rd menu page, and find that I rarely go there, as the 16 items on the 2 pages is really enough.