Having downloaded this fab template today, i also had trouble editing and customising the road signs, but found the answer – no one has bothered to anwer this properly anywhere except for the person who designed it.

All you need to do is go to LAYOUT, then click on PAGE ELEMENTS. You will see (header) bar then underneath should be menu which you can EDIT.
Click on EDIT, enter what title you want, eg HOME, add the link for your home page in New site URL box or whatever you want it to be.
New site name: ‘HOME’ (or whatever you want to show in the road sign).

There’s space for 4 titles, so type 4 into the Number of links to show in list box.