I want to know how to tackle someone suffering from phobia of walk. It sounds weird that anyone can be suffering from the fear of walk
Exposure therapy is the most effective treatment for phobias (it has been found to be more effective than cognitive behavioral therapy, medication, and insight therapy). It's important that the therapist break down the steps into a hierarchy of exposure exercises. Initially one can change various dimensions to be less intense by increasing the proximity to the triggering scenario, decreasing the duration of the exposure, lowering the feared characteristics of the triggering element etc. One can even start with visualizations first (or virtual reality simulations, in some cases).
If the phobia is too strong, one can add coping elements such as a support person, a minor amount of tranquilizer, positive self-talk and/or relaxation techniques during the exposure.
Consistency is key. For more info, see
Bourne, Edmund J. Overcoming Specific Phobia: A Hierarchy and Exposure-based Protocol for the Treatment of All Specific Phobias: Therapist Protocol. New Harbinger Pubblications, 1998.
For a patient with a walking phobia the exposure can be gradually increased in intensity by increasing the distance walked (it may initially be virtual or just one single step). To extract further degrees of freedom, it may be necessary to discuss it in more detail with the specific patient.