Can't put my new music I bought on my iTunes
The most likely problem is that your computer isn't logged in to the same AppleID as the one you purchased the music under. Go to System Preferences→iCloud and check which account you're logged in as. Alternatively, in iTunes look in the Store menu. One of the menu items will be "View Account (your_account_name_here)". If the account is correct, from the same menu select "Check for Available Downloads".