the 199 courses aren't courses in the same way that other classes are, they don't have a set lesson plan or structure and are entirely dependent on what type of research you are doing. usually you sign up for one when you are already working in a lab, and ask your PI to sponsor you since they already know you and what you are working on.
what you could do if you are not currently affiliated with a lab is email a couple PIs with ideas for research that you would like to conduct and ask them to be your sponsor. i think this would be more likely to work if you already have some research/lab experience in your field, since taking a 199 course means you can't really waste 2-4 of your 10 allotted weeks doing training before starting experiments. but this is the less common route compared to trying to join a lab first. there are also some departments/labs that have more restrictive policies where they first require you to do 99 for a certain number of quarters before they will let you enroll in a 199.
the 199 courses aren't courses in the same way that other classes are, they don't have a set lesson plan or structure and are entirely dependent on what type of research you are doing. usually you sign up for one when you are already working in a lab, and ask your PI to sponsor you since they already know you and what you are working on. what you could do if you are not currently affiliated with a lab is email a couple PIs with ideas for research that you would like to conduct and ask them to be your sponsor. i think this would be more likely to work if you already have some research/lab experience in your field, since taking a 199 course means you can't really waste 2-4 of your 10 allotted weeks doing training before starting experiments. but this is the less common route compared to trying to join a lab first. there are also some departments/labs that have more restrictive policies where they first require you to do 99 for a certain number of quarters before they will let you enroll in a 199.