Newbie question: include paths

[Emmanuel King Turner]

Heyas,

I'm new to KDevelop, but I like what I see!  My problem is that whenever I
compile a project, it can't find certain include files that it needs (eg
qvariant.h).  I definitely have these files on my HD - and for a working
version of qt2 as well.  I'm just wondering how to "point" KDevelop at them. 
I've been ripping my hair out over this one for sometime, I've considering
modifying the project makefiles by hand, but surely there is a better way.

--Et