ok, so connect it to ur computer.. open up the ipod software or w.e. it is (i dont have an ipod so i dont know), and from then on i think its like common sense.
or plug it into a computer with no music in itunes or whatever music u have in itunes and itll say something along the lines of would u like to update your ipod to this computer or something and if u click yes itll delete all the old songs and put in ur new songs from itunes