Hiyas =)
A couple of things. One depends on what custom UI you are running. For example if you are running Fetish, Zonx has specific instructions for installing eq2map and his mod in order to get them to work together. So if you are using a *package UI* like Fetish. Thor, Extreme - check the documentation for the UI or ask in the specific UI thread.
But, if like me, you are running a compilation of pieces (with no custom map UI pieces) you might just be going about it the wrong way around.
First you need to create a custom UI dir. See how to do that in *this* thread
installing faq
THEN install EQ2Map - as it looks to eq2.ini for *directions* on what UI is automatically loading when you open the game.
Thats the easiest way to do it. Depends on the savvyness of the person doing it, you could also just create your custom UI dir now and move EQ2map into it taking care to merge items in the image folder and not just overwrite it.