To exports your logged raid from the WoW addon to a xml string you simple need to make a right click on the raid and select "Show xml String".
Then there will open a small textbox with the string preselected, you only have to press ctrl+c and have the string in your clipboard.
Now you can past it to your dkp system.

Example XML Strings for MLdkp 1.1 (Formatdescription):

Example XML Strings for EQdkp/EQdkp Plus (Formatdescription):

This string could be imported by EQdkp CT Raidtracker Import Plugin (DE-Wiki)

Example XML String for MLdkp 2.0 (Formatdescription):