To enable navigation without a mouse, you need to turn on the high-contrast color scheme in your Preferences settings.

To turn on high-contrast color scheme:
  1. Navigate to Preferences by clicking Your avatar > Preferences.
  2. Click General Preferences.
  3. At the bottom of the page, click On in the high-contrast color scheme field.
  4. Click Save.
  5. If you are using a Mac OSX environment, you also need to turn on all "All controls" for full keyboard access by naviagting to System Preferences > Keyboard > Shortcuts and select All options at the bottom of the dialog.
  6. If you are using MAc OSX, you can enable voiceover capability by navigating to System Preferences > Shortcuts > Accessibility and select Turn VoiceOver on or off