Network Access From Home

I have a small network of a Windows NT 4.0 Server and 10 win 95/98 clients. We run a lotus Notes server on the NT. The LAN is connected to the Internet on a fractional T1 with a Cisco 1720 router and a SonicWall firewall. My question is how can I access the office network from home and use the applications in the office as if I’m using a local machine. Please be detailed in your answer if possible. Thanks.