DESUMA is a Java based program to allow users of the UMDES library to view results graphically. If you have not done so already, you must download a copy of UMDES before proceeding any further.
Before initiating your first DESUMA session you must point DESUMA to the UMDES library, to do select the Edit | Preferences... (or on OSX Desuma | Preferences...).
From here, select the browse button located next to the plugins directory, then A file chooser will open. Now locate the file where the library is located. This folder should contain the umdes folder which contains a file called umdes.xml. Once this is done click open and then OK and the plugin will be automatically loaded every time you launch DESUMA.
One thing to mention is that on Linux/Unix/Mac systems, if the plugin library consists of executables you may need to change the file permissions of the files. (only once though) You can fix this by going to the directory of the executables and type in the command line "chmod +x *" or through the File Preferences for your operating system.