Start In an More Up Right Position, Then Simply Lean Towards the Wall Ending in a Similar Position Shown By Our Model & Hold the Stretch At a Point Where You Feel the Tightness Focused in Your Calf.  Repeat with you other leg.
Note: If You Slightly Bend the Knee Which You Are Stretching, You Will Target the Deeper Calf Muscles (the Soleus Muscle)

Gastrocnemius Muscle Graphic
Soleus Calf Muscle Graphic (Note that the Soleus muscle does not cross the knee joint) Soleus Muscle Stretch
(note: this muscle does not cross the knee joint as does the gastrocnemius.)
more calf stretching techniques

Ankle Sprain Treatment and Rehab.