How do I configure Google Drive to not sync everything to my desktop?

Everything will sync to your Google Drive folder unless you choose to sync individual folders.

To do this, click on the Google Drive icon in your computer’s taskbar or system tray, then select Preferences. Then check the box next to "Only sync some folders to this computer."

Select which folders you'd like to sync to your Google Drive folder, then click Apply changes. The folders you do not check will not sync back to your computer.