So far you have been posing both legs at the same time. It is possible to
pose one leg or arm first, then copy and paste it to the other side.
3 In the Front viewport, select one calf. Scale the calf so the ankle joint
falls just above the bottom of the pant leg.
4 Scale the foot so its bottom reaches the bottom of the mesh foot.
Aligning the Biped to the Model | 903