Go into a patient's clinical notes and select the "Scripts" tab. Search for drugs by typing part of the drug's name in the orange box.
Click "Add Drug" and fill in the required details.
To delete a drug, select a drug and click the "Delete Drug" button.
To add new instructions, select the drug and click on the "New Instruction" button in the top panel. Alternatively, right click on the drug and select "New Instruction" from the menu. The "current user" option allows you to create an instruction that only you will be able to see. "All users" allows you to create an instruction that all users will see.