Preparing for supplementary exam is no different. You have one subject and try to read it and also don't lose confidence.
How much time do you have?
Do you have Past papers?
Do you have senior help to know important topics?
Get your notes ready, a course book and a reference book.
A paper to practice diagrams and flowcharts of mechanisms.
If you have a study partner, get into revisions.
Target to revise the subject atleast 3 times before final reading.for exam. Focus out other subjects for now and focus on Physiology.