Download the lyric from internet and use the ultrastar creator program to sincronize the text with the music, with this program you generate a file to import in EOF with the lyric import option (F8), here you need to syncronize again the text with the music (song>track>Part vocals) why? probably because you add a leading silence at the begining of the song (use the option select all to move all at the same time), and after save you have a xml file, this xml file generated in EOF is needed in rocksmith toolkit to add in the RS file.
jcobreti's post in How do I go about obtaining lyrics for song in EOF? was marked as the answer