Estimating the credit spread

hi sir im following the bpp course notes and in ch 7 they have "estimating the credit spread" which i didnt understand from their notes at all. i was trying to find a lecture in open tution and the topic in the open tuition notes as well but maybe ive missed it. if you dont mind telling me which chapter this topic is in the open tuition notes and under which chapter do you cover this in your lecture videos. thanks alot.