Park at the Glover arms/dobies garden centre, it's just after Tesco then when you come out take a left at the roundabout go down to the inveralmond roundabout and go right round it and head back up towards broxden.
Looks far on the map but it's only really a 5 mins walk.
The other option would be to park in one of the street in Letham and go over the hill and down to broxden that way. Might actually be better traffic wise