It entirely depends on your budget! You can take a direct flight from Bhopal to Kullu (Bhuntar): goo.gl/Z67dw3 .From where Kasol is an hour away. Taxis are easily available at the airport. If you are on a budget, then reach Delhi, and take an overnight bus (AC or VOLVO are easily available and don't cost more than Rs 1,500) to Bhuntar. From where you will have to take a shared taxi or an HRTC local bus.