Its very simple.. first off there is no debian installer for PS, its a compressed file (tar.gz). Uncompress the file, by right clicking and selecting 'Extract Here'. When looking in the folder you'll find a file called 'photoscan.sh'. This is a simple bash script that acts as the executable to launch PS. Double click on the '.sh', and as long as its permissions are set to be executable, a selection of options will pop up, click 'run' and PS will launch.
Alternately, open a terminal, navigate to the folder and execute the '.sh' by typing ./photoscan.sh
This will allow you to see if there are any issues on launching.
hope this helps
Mike