Thanks Patrick R for telling us the name of the directory.
Unfortunately I must agree, that this video is more a demo of piwik, but not an installation guide.
Installing of php/mysql apps are almost the same procedure: upload, create db, run install procedure (by opening the url).
But I could not find the hint with the tmp-directory anywhere but in Patrick R's comment. This should really be added to the FAQ.
Patrick (August 9) as soon as you ad a directory tmp, the error message will make sense:
chmod 777 /home.../.../piwik/httpdocs/tmp
But why is this directory not included in the zip? It would make life so much easier for all of us ;)