First, get to Rawalpindi Daewoo bus station.If coming from Rawalpindi, it wil cost only bout ruppees 80 to 100 to the station. Then buy the ticket to Abbottabad, the fares is bout rupees 130 per person and the schedule is about every 2 hours or so.It will take 2 hours plus to Abbottabad. Then, once you reach there, get a van to Mansehra for only rupees 20 to 30 per person in a 12 to 16 pax van. It will take about 30 minutes from Abbottabad.
Buses to Mansehar operate from all over the country..You can either use a cheaper way which is normal bus service or luxury buses with air conditions. This is recommended. Its bit expensive than other but less hassle.For all the information on bus services & timings plz follow the link below: