You need to go to the Mac you want to access and under System Preferences->Sharing activate the following:
On all this options you can limit the users that can have access.
On the File Sharing option, you can determine what folders can be accessed in the network and by whom.
On Remote Management you will be asked what you want from this list, use option/alt click to select all:
Once that is done you can go to the other Mac you want to use and in Finder you should see the Mac on the sidebar under Locations or click Network:
You see on the top right options to Share Screen or Connect As. Click Share Screen to get remote control of the other Mac or Connect As to simple browse the folders that you gave permissions on the File Sharing step.
