In iTunes, select File, then from the drop down "Add file to library". This should open a dialogue box in which will be listed your downloaded songs. (Limewire puts songs by default into "Shared"). Highlight the song you want then select Open, the song will be imported to iTunes and (I think ) converted to play there. If you have a lot of songs, go to the shared location, make a new folder and in the previous step on the drop down, select Add folder to library. Select the aforementioned folder and all the songs you previously moved into it will be moved into iTunes.