To add questions to your quiz, go to
Components->BF Quiz Plus->Questions
Press New button to create a new question
Select the category for your question (effectively which quiz will this appear in)
All the fields with asterix next to them are mandatory and must be fill in before you can save the question.
For users that have previously used BF Quiz for Joomla 1.5, you will notice that some of the more advanced fields have been moved into the expandable section called Advanced on the right hand side below the options.
The below sections go into detail about each of the fields on the question form.