I have an updated brother of DEVC++ called wxDev-C++ - but I think the layout is very similar.
You bring up the project options dialog box, select the directories tab, and on that screen
there are sub-tabs where you can add additional directories for libraries and Include header files .
There is also a tab called commandline options - and on this screen on the bottom right there is a button called "add library or object" - use this to add additional libraries to the project.