Q: How to setup iMac and macbook pro for sharing

I have an iMac desktop running El Capitan and a MacBook Pro runningMavericks. I would appreciate someone guiding me thru the step by step procedure for being able to share between those two platforms.

I know I should probably update the laptop to El Capitan, but just don't have the time to do it now.

Thank anyone for their advise and guidance in advance.