new to coding

I have a few questions. I am new to coding and am unsure of some things. Say a patient comes in to the office from an urgent care and has a fracture. My dr gives the patient a boot, can I bill for the boot for this 1st visit?

Next if a patient is in the global period following a knee arthoscopy and receives an injection, do I only code for the injection meds such as depo or synvisc? I know the injection site such as 20610 is not billed. Also do I use a 58 modifier?

new to coding