A 75th minute substitute in Saturday's preseason 1-1 friendly draw with AC Milan in Dublin, winger Harrison was jeered by Leeds fans.
Harrison spent last season on-loan with Everton and had plans of signing permanently with the Toffees.
"It (the boos) wasn’t a surprise," Farke admitted. "It was expected with his first outing in front of such a large amount of Leeds supporters. Our supporters have the right to have an opinion and it was challenging for our supporters with his decisions.
"But I also liked the reaction of the others, who clapped whenever he touched the ball. It’s still up to Jack to win everyone over - to show commitment, to show desire and be brave and this is the best way. He has presented himself within the group as a top character and he has all the chances to win our supporters back.
"You could feel that he’s won a few back already because after the boos, others were clapping. Jack has all the chances to prove that he can play an important role for us in the upcoming season."