I just received my new iMac desktop, 24”, and I don’t understand how to attach my canon printer and my ethernet cords?

You'll need USB-C to USB adapters to use your Canon printer.

USB-C to USB Adapter - Apple or you can try something like this:

(google USB USB-C adapter)

If you bought the middle or upper tier iMac, you'll find the ethernet port on the power block.

Otherwise, you'll need to purchase a Thunderbolt to ethernet adapter.

Thunderbolt to Gigabit Ethernet Adapter - Apple

For your printer is it Wifi or does it support Airprint?

The base 24" iMacs do not have an Ethernet connection. The Ethernet connection is an option for these when you order the ocmputer or if you buy a more "specked out" 24" they come with Ethernet. The Ethernet connection is on the power adapter. Please refer to https://support.apple.com/guide/imac/take-a-tour-24-inch-imac-apd2e7352054/mac and review where it says:

• Gigabit Ethernet (RJ-45): Ethernet is built into the power adapter included with the 24-inch iMac with four ports. The 24-inch iMac with two ports comes standard with a power adapter without built-in Ethernet, but can be configured with Ethernet at the time of purchase. To use Ethernet, connect a router or modem to the Gigabit Ethernet port on the power adapter.

How do I connect USB cord to 24” iMac?

You need a cord with a USB 3.0 plug which goes into a socket on the rear of the iMac, if your peripheral only has a bigger USB plug you need an adapter as shown in an earlier answer.