You will need to provide lot more detail in order for people to provide meaningful assistance in this matter.
Detail such as:
What troubleshooting steps have you tried?
What error messages are you getting?
What are you using in order to connect?
Is this for a connection between devices on the same network, or is this a remote connection to a computer on a different network such as an office?
Does your firewall currently allow for remote desktop connections, both inbound and outbound on both machines and the network itself?
With these questions answered, hopefully myself or another community member can assist you.