How do you change from 1 wheel drive to 2 wheel drive

Hi,
The manual is at this link:
http://www.managemyhome.com/mmh/lis_pdf/OWNM/L0312022.pdf
And on page 50 it shows that a bolt and nut fasten each wheel it its repsective axle end. Early versions used what was called a klik pin which could be substituted at greater expense (a corner cut to save a few cents on the part of the manufacturer.)
Peace,
Clarke