Q: How do you get music bought on iphone itunes into my imac itunes

Assuming you have later software than your profile indicates above (it says iOS 4.3.2, which is now about five years old), open iTunes on your computer and use the menu to go to iTunes > Preferences > Store and select "Automatic Downloads - Music".  That will download future music purchases you make on your iPhone to your Mac.

To download previously made music purchases made in the iTunes Store from your iPhone to your Mac, use iTunes' menu when the iPhone is connected to iTunes to go to File > Devices > Transfer Purchases.

Again, hopefully your iPhone is current with its iOS version, and your iTunes is current as well.

There are several ways:

Redownload or transfer your iTunes Store purchases from an iPhone, iPad, or iPod to a computer - Apple Support

Sync media between your iPhone, iPad, or iPod touch and iTunes on your Mac or PC - Apple Support

Sync your iPhone, iPad, or iPod touch with iTunes on your computer using USB - Apple Support

Usually this would work:

Transfer your purchases

Before you transfer your purchases, make sure that your computer is authorized with the same Apple ID you used to make the purchases. Learn how to authorize your computer using iTunes.

If the content that you want to transfer was purchased using multiple Apple IDs, you'll need to authorize your computer for each one.

To transfer purchases from your device to a computer, follow these steps:

1. Connect your device to the computer. Wait for its icon to appear in the upper-left corner of iTunes.
   
2. From the menu bar at the top of your computer screen or at the top of the iTunes window, choose File > Devices > Transfer Purchases from "[device name]".
   If you’re using Windows and can’t see the menu bar, learn how to turn it on.

​​This feature works only for content purchased from the iTunes Store. Any items that you import from audio CDs or receive from other sources won't transfer from your device to the iTunes library. However, all podcasts from your device's Podcasts app and copies of all PDFs, books, and audiobooks from your device's iBooks app will transfer to your computer. Learn how to transfer media to your iTunes library.

Glad that helped.  Enjoy your Apple gear.