how can i transfer my own songs to the ipod?

My dad gave me his ipod shuffle and he has his songs on it. Ive got the USB. Ive downloaded the latest itunes.... I cant seem to find anywhere to transfer my own songs onto this ipod. My music from my own computer has been tranferred to Itunes. Looking at answers it seem that I need this 'autofill'. The only thing im also worried about is when i connect my dads ipod it says that its syncd with another pc, do i want to erase this ipod and sync with this library instead?''.

1. will this delete my dads songs??
2. Do i need to OK the erase to transfer my songs onto the ipod, and for autofill to come up??

Please please help... my dads not a clue how he put them on in his house lol!!