Discover remote acces
There are numerous solutions for using a Mac to monitor and control another remotely, and one’s built into OS X. On the Mac you want to share, open Sharing in System Preferences and turn on Screen Sharing. On the other Mac, you’ll see the shared Mac in Finder’s sidebar. Select it, click Share Screen, and input an account name and password for the remote Mac before clicking Connect. Whenever your cursor goes within the window displaying the remote Mac, it will control that machine.
Need to control a Mac over the web? You can use iCloud if both Macs are signed in with the same Apple ID and password. In iCloud within System Preferences for both Macs, ensure you’re signed in and turn on Back to My Mac. (Access to the remote Mac is still done through Finder; select Back to My Mac and then your Mac from Shared.) This service requires a router supporting NAT Port Mapping Protocol (NAT - PMP) or Universal Plug and Play (UPnP) – an AirPort Extreme will be fine – and a firewall that allows remote connections.