Make sure terminal services is installed on the server you wish to connect to. Once installed, terminal services gives you the ability to create a client software disk. Use the disk on your client.
Since you will only be having 1 server this will simplify things. The server will have a public ip address. You can connect to the internet with a client, and after installing the client software from the disk, you can open a session to the server's ip address.
Security under this scenario is terrible, given you will be transmitting confidential information (time tracking, etc.). You can improve your security by encapsulating your terminal session inside an encrypted VPN connection... i.e. L2TP with IPSec policy. Yes, it does use more bandwidth, but the security is worth that. Bandwidth isn't massive in terminal services, I've done it over a modem connection with good results.
Also note that in the domain controller's OU, the default domain controller's policy limits log on locally to specific groups. Terminal services is considered logging on locally to the server with terminal services. Any user who is given the error message "can't log on interactively" doesn't have the log on locally permission.
Terminal services gives you two installation options. The administrative mode allows 2 concurrent connections. If you need more than that, you'll need to license the connections.
