Choose an instrument, make a new pattern, open the piano roll, hit the little button for the countoff and record by toggling the record button and hitting play. Afterwards, you can quantise (start times for example) from the dropdown menu in the piano roll.
It's kinda weird i can't help. I never used FL studio just because back in the days when it was called fruity loops most producers disliked it. But nowadays it's on the top of the list i gotta say the top is deserved for fruity loops life long free updates when purchased. But it shouldn't be hard to fix the issue you have there.