How did they put the wooden piles into the loch?

They sharpened the bottom end of the pile to a point using axes. They tied a cross piece of timber and attached it near the top. A person on either side of this cross piece could then twist back and forth to drive the pile into the bed of the loch.

This question was answered by:
Barrie Andrian MIFA, FSAScot, The Scottish Crannog Centre (UK)