Question

Where does the friction act on our feet while we are walking?

Answer 1

When we walk, a force called friction builds up against our direction of motion. 
It acts on the sole of our feet, which is the part which touches the ground while walking.

Answer 2

Of course every force has an
equal and opposite reaction:
there are equal and opposite
forces on your feet and the
ground at their point (area)
of contact.