Iphone and OS X recognition

[Allegra475]

I've got an iMac with OS X, software version 10.5.8.
The itunes on it is version 10.6.3.
I have an iphone 4s.

When I plug in my iphone, itunes will recognize it, but I cannot move music from my library to my phone. It just bounces back. I've seen lots of posts that say the phone isn't even recognized, but that doesn't seem to be my problem.

I inherited this computer from someone, so I feel like a total newbie here.
Thanks for any input.

 

[Kaveman]

You need to set the Manage Music Manually checkbox

 

[Allegra475]

Where is that option?

 

[Allegra475]

Okay, I found that option on my phone, but when I clicked that it gave me the option to sync and erase all of the music that was already on my phone, which I don't want to do, because it's not on this computer in the library. Does that make sense?