how do you access system preferences with the keyboard?

Use the key comgination of ⌘+space bar to bring up the Spotlight window. Then type in System Preferences and hit the Return or Enter key. That will open that app.

Or enable and use Mouse Keys:

Change Alternate Control Methods preferences for accessibility on Mac - Apple Support

You can also use Control - F2, which will move the focus to the Menu bar.

Use the down arrow to navigate to System Preferences…, then press the Return key: