hi,
to used icloud you need to have osx Lion installed on your mac pro.

http://itunes.apple.com/us/app/os-x-lion/id444303913?mt=12

to be sure your Mac pro has iCloud active, go to system preferences --->> icloud, sign in and select the services you'd like to enable.

also if you want to do sharing or automatic update for all devices.
open iTunes and choose Preferences. Then click Store and select Music, Apps, and Books.

for more information go here --->> http://www.apple.com/icloud/setup/mac.html

let me know if you have any more question

icloud dont sync music

that why you did see it on iCloud

you can only using home sharing setting on itunes and thats it

you can turn on automatic download music and app

in itunes, edit --->>> preferences

store tab

or doing home local share on the share tab

but you cannot sync itunes on icloud

if you have other question, let me know

if not please click accept. thank you

did you sign in on your mac pro?

make sure you update to the latest itunes version

if you have check the box automatic download new music before you make the purchased

then it will no download it

you have to manual download it by click on the app store on itunes on your mac pro

then on the quick links

click purchased

select music tab

and download the song you purchased before you select the automatic download

make sure you check automatically for new download

you can force quite itunes

by click on apple logo

then force quite

or shortcut key Option-Shift-Command-Esc