The yellow text indicates a rollover which will provide a definition of the word.
The yellow highlighted number at the bottom of the screen indicates the page you are currently on.

Clicking on the black left pointing arrow at the bottom of the screen will take you back to previous tutorial page.

Clicking on the black right pointing arrow at the bottom of the screen will take you to the nest tutorial page.

By clicking on the next number beside the highlighted number will take you to the next page in the tutorial.