Nearly there. If you haven't downloaded a copy of the Armory git repo (the code), you'll need to do that. Can either grab the zip and extract it or git clone if you're familiar with that.
Either way, once you have a copy of the code, cd to wherever the Armory code is.
Then run step 7 again:
cd osxbuild
python build-app.py > /dev/null
Compiling may take a little while

Fingers crossed!