Tick one or more highlighted topics, choose how many questions, then press Start quiz. Your score for each topic appears under it after you finish.
Questions you answer correctly are set aside, so you mostly see ones you have not mastered yet. Once you have all of a topic right, it resets.
HL students see every topic; SL students see only the SL/HL (core) ones. The HL-only material is tagged (HL).