Drag the mix on the tarp to the spot where you want to build. Anywhere is fine. If the foundation is low enough, two people can roll the mix off the tarp and up onto the foundation. If the foundation or walls are too high to roll the cob up onto, you can make a ramp to drag it up or lift it by handfuls, tubfuls or buckets onto the foundation.
If you haven't already put the pipes in for the electricity and plumbing, now is the time to do it!