Below and also here is a link to an excellent article on plantar fasciitis. I’ve given you yoga postures to help with strength and flexibility to assist you.
For strength: Tadasana or Mountain Pose
Standing with feet slightly apart lift all ten toes to feel the arches rise. Press into the base of the toes. Look at them. Are the little toes coming up as well? Put toes down and maintain the lift of the arches. Lift the arches of the inner knees, the inner groins and lift the inner arches of the hip bones. Pick up the skin of the legs and feet. Pick up the abdomen. To increase awareness, raise your arms, firm the muscle to the bone and pick up the skin of the chest. Soften so there is action without strain. Feel and hold the memory with steady breaths.
For flexibility: Vjrasana or Hero Pose and Modifications
Kneel on blanket with knees together. Press calves back and sit on heels. Re-position by lifting hips and holding heels together to sit back again with sit bones behind heels which will press the heels forward. If the ankles can stretch more, put a rolled blanket under toes and sit again. If the ankles are tender and need support, put a rolled blanket under the ankles and sit again. If the knees are stiff have another rolled blanket behind the knees or a folded blanket under the buttocks between the feet. Binding the ankles with a strap is the final stretch for the inner ankles but not necessary. You just need manageable sensation. To stretch the outer ankles more, come onto the knees and turn toes in so big toes touch and sit back with feet parallel to buttocks. Feel and hold the memory with steady breaths.
For flexibility: Malasana or Squat
Kneel on blanket with a rolled blanket beside you. Raise knees to squat and slide rolled blanket under your heels. Lean back and raise trunk and raise arms to parallel. Draw the shin bones in and the inner groins back. Lift the abdomen up. If the knees are tender have another rolled blanket behind the knees when you are on your shins. The knees will bind the blanket as you rise up. Feel and hold the memory with steady breaths.