I think you mean thedrive belt seems to be slipping.
This may help:
http://howtomendit.com/answers.php?id=192781
http://www.diynot.com/forums/viewtopic.php?t=159284
http://www.fixya.com/support/t2803800-fitting_new_belt
Screws holding the top on are probably at the back. If so it's probably undo sc=rews, lift back of top and slide forward then lift off. Remove the soap tray first.
Google is your friend
X, June 2015