That little munchkin really is pointing up!! I'm sorry but I really don't know how to flush soil but I'm sure you can find the info from these threads--I would imagine simply use ph correct water water heavily until the water draining through the bottom runs clear. After that tho, I draw a blank.....
(Truthfully for that question I would find someone else's opinion better than mine) but I would not add any nutrients to your water for now for sure. Also make sure your ph is ok (about 7 for soil) Ususally good potting soil is already ph correct but never hurts to check....