The Holland youth international was close to joining the club before the summer deadline, but a problem with his medical delayed the deal.
The 19-year-old's injury problems, though, have not dissuaded Jol from making him Fulham's first January signing.
Jol said: "First we have to get him fit and after that you will see he is an international player at all levels.
"I am very happy we have got him. He has signed and he is here. He is 19 years of age, player of the year of all the academies in Holland.
"He is an exciting talent but he will need at least six months of a year to adapt. Hopefully he will do it quicker. He is a very, very good talent.
"People say Ajax were interested and I imagine there will have been other clubs who were interested in him."
Jol would not be drawn on reports of an imminent work permit hearing for Dnipro midfielder Derek Boateng, saying: "We won't mention names, we won't speculate and we won't tell you until something happens."