As with every other injury or health issue, you have to be very gentle when you do exercises with PF. Luckily yoga offers various poses that gently help you stretch the plantar fascia, which in turn, can reduce the pain you experience. A very popular yoga pose that can help with PF pain is the Downward Facing Dog pose, for example, or the Hero's pose. Focus on poses that will help you with those tight calves and Achilles tendons!
Before you go and get started, a word of caution - I am by no means a yoga specialist. In fact, I just recently have started practicing it myself, and I thought I share my experience with you. So, please, before doing any yoga pose, go get yourself an experienced yoga instructor who can show you how to do it the right way. I also don't recommend only following instructional videos (unless you already are an advanced yoga practitioner). Remember, you don't want to cause additional damage to your feet!