I doubt it even is possible to insert new names for maps in AdvanceMap, the best thing to do is change them. But maybe it could be possible with a hex editor if you know how to use it. But so far... I haven't found any way of adding in a new name, I've only been able to change the names, that's about it, I'm sorry if I couldn't help you very much.
EDIT: Wait... after double checking your post... I see that you want to change the name of the map and the map itself, I see. Well... in AdvanceMap to change a map, click Tools then click Open map, then choose the map that you've saved and open it up. As for names... you can just change them on the Header tab. It should have an area where you can simply re-name it, after you've typed in the name, click change name button.
Other than the fact that when you change the name of the map it ALSO changes the name of Littleroot Town to what ever you changed it to.