If you go to the homepage of the specific tournament, there is a withdraw option on the right hand side of the page.
remove myself from Tournament

also in your unrated games you may simply resign each game if u dont mind g ames lost tally increasing

There is a huge drawback, as in the past I was pushed into a tournament that I did not remember signing up to - in my notifications I said no tournament, yet i lost ten games without even playing one!
I had been winding down my chess games to fo on holiday at the time
Does anyone know how to remove yourself from a tournament?