By now you should have a general knowledge of Simming. As the Medical Officer onboard a Starship, it would be of great benefit to you, to review information on StarTrek Medical Science. It will help you to become more familiar with the instruments and tools and how to use them. For Example: Use a Dermal Regenerator to heal scarring and burns, etc. Also, review the crews BIOS's and look over their medical history, so you'll know how best to go about treating them.
The Medical Department is responsible for the health and well being of all the crewmembers as well as any visitors should someone become injured, it would be up to the Medical Team to heal them. The Medical Team also must come up with solutions to rid the ship of viral infections should the crew come in contact with them. As a Medical Officer, you are to provide medical assistance wherever it is needed. It is your Prime Responsibility.
When the Medical Department is not busy with one of the above situations, try treating ghost players. For example, you could treat a ghost player with the common cold, or even deliver a baby :) Should the ship come in contact with Aliens, do your best to look up information on the Alien Species and prepare the ship for a medical emergency. If the Captain orders an away team, request to go with them, but if permission is denied, work with the Science Department, to make sure the Away Team will be safe.
As the Medical Officer you have the authority to keep injured, or sick crewmembers in the Medical Bay until you believe they are capable of returning to their duties. For example, if the Captain contracts an unknown virus, you should not let him return to work until you have come up with a solution or cure to the virus, or until you have determined that the virus is neither contagious or deadly. Best of luck, & keep those crewbies healthy!