Ruiz, 26, joined from FC Twente for a fee believed to be in excess of £10million to become Jol's seventh summer signing at Craven Cottage.
The Costa Rica international told the club's official website: "I know that a lot is expected of me but I'm here to make a difference - I want to do all I can for Fulham.
"This is an exciting challenge for me, possibly the biggest of my career so far. I have signed for a team that is continuing to grow and one that offers so many possibilities."
Despite the reported large fee, Ruiz is not worried about playing in what is perceived to be a tougher league than Holland's Eredivisie.
"The club paid a lot of money for me, I know that, but it is a responsibility I am willing to carry. I will react positively and hopefully I can take the chance that I have been given," he said.
"There were a number of things that attracted me to Fulham.
"Of course, there was the chance to play in the Premier League and for a manager that I have a lot of respect for. I know the way he (Jol) works and I'm confident that I can do all that he wants me to."