Here you can see that the bike route starts inside the terminal!

Viewed from Passenger Pickup, these are the bike signs that mark the route (look at that hot sun and plan to bring water!):

This is the only bike parking I saw at DIA, making me think there is either an employee shed somewhere or they mostly envision this bike route for travelers.

Here are examples of the signage along the road:

This route is not for the faint of heart. People who have done it report that riding so close to cars zipping by at 70 is nerve racking (but something they would do again). Still, I'm just happy that some facility has been made to make a distant and rather inaccessible airport more accessible.
MassBike has information about riding your bike to Logan.