You would have to take the road route from Shimla to reach Sangla. From Shimla, Sangla is an 8 hr drive (for first time drivers this time may be around 10 hrs).
From Chail/Shimla to Karcham (the turnoff point on NH 22) is 221/209kms. Please take a right turn at Karcham. And at around 18 kms down the road, you will hit Sangla. 6 kms ahead of Sangla you would spot the "Banjara Camp" sign on the right. Take a right turn from here to reach the Banjara Camp parking lot at the base of the hill.