So as to do the Online Practice Test for FCE Free Sample go to
http://www.buenosairesopencentre.com/main.php
Click on ALUMNOS on the top right hand side
Then click on FCE which is in green on the left
Scroll down and under the heading SUPPORT FOR FCE
Click on Free Online Practice Test Sample
Or just click on
http://olpt.s3.amazonaws.com/online-practice-fce/index.html
Hope you find it useful