1) Put the lensflare folder in the viewer folder.

2) Connection: add this line in the tour.xml file
  <include url="%VIEWER%/lensflare/lensflare.xml" />

3) Add the expression ?initvars.setflare=true to the url in your browser

4) Follow instructions given in the console

6) Start browsing normaly, without the expression ?initvars...