as far as I remember, you have to put the new wad (the one you want to use) on your mmc card (not in a folder, just on the card).

Do this thru USB connection and transfer it from your PC to the nokia's mmc card.

enter xterm
sudo gainroot
Now, you have to copy (cp) the file from your mmc card (/media/mmc1/name of your .wad) including the .wad extention at the end of it I think
into the doom .wad folder (/usr/share/lxdoom/wad)

something like this command:

cp /media/mmc1/nameofyour.wad /usr/share/lxdoom/wad

try mmc2 if it doesnt find it,
or try the move (mv) command

cd /
(will get you to the base of your file system)
cd media/mmc1
(will get you to the base of your mmc card
ls
will show you the files on your mmc card- check to see if your wad is there...

because you are now navigated to the place of the .wad you want to move,
I think you can just do the move command with the direction of where you want to move the selected file:
mv (nameofyour.wad) /usr/share/lxdoom/wad

and you can even check in the doom wad file to see what is there by
cd /
(will get you to the base of your file system)

cd /usr/share/lxdoom/wad
(will get you to the doom .wad folder)

ls
(will show you the contents of that folder.

I am not sure how familiar you are with navigating and manipulating files via terminal,
but anyone who is familiar is probably laughing their asses off at how lame I am....

Hope this helps, write back if you get error messages!!

dcarter