This is a work computer and I'm trying to change it

To change your work computer to Windows, you will need to obtain a Windows installation media and install Windows on your computer.

Here are the steps on how to install Windows 10 on a Dell Optiplex 9020:

1. Back up your important files.
2. Create a Windows 10 installation media. You can download the Windows Media Creation Tool from the Microsoft website.
3. Boot your computer from the Windows installation media.
4. Select the language, keyboard layout, and time zone.
5. Click on Install now.
6. Select the type of installation you want. If you want to keep your files and settings, select Custom: Install Windows only (advanced). If you want to erase everything and start fresh, select Delete all partitions and create new ones.
7. Select the drive where you want to install Windows.
8. Click on Next.
9. Windows will be installed.
10. Once Windows is installed, you will need to create a user account and set up your computer.