You need a Windows XP installation ISO. A good working image is archive.org

You can check the SHA1 hash on Mac in the terminal using the following command,

shasum /path/to/file

Here are the steps to reproduce the installation of the image,

1. Open the downloaded template .utm and double click it
2. At the bottom of the screen is CD/DVD with an option to select an image
3. Select your Windows XP installation ISO
4. Start the VM
5. Install Windows XP with all the default options
6. After installation, download the SPICE tools ISO
7. Eject the Windows installation ISO, and select the SPICE tools ISO
8. Install the SPICE tools