You need to have public ip to access that sql server machine. If your server is located behind firewall, u have to configure firewall to redirect to sql server with specific port (default is 1433) then using enterprise manager to connect to that internet ip.
Another way is to use VPN connect to your office network and use EM like u sit in the office.
Thanks so very much,Devmonk. I tried it through firewall via port forwarding, but failed. I’m trying on it, will let you know.