I was getting at "remote access" is a very general term.
Microsoft loosely uses the the term "Windows Remote Access" and it variously applied to any one of these 3: Remote Dialup, VPN, or Remote Desktop. Third-party Windows partners also use the term for some products, for example: Citrix, BackToMyPC, etc.
Assuming that you mean one or more of the basic three Windows Remote Access methods...
If you were using Windows RAS dialup, you need to purchase a USB modem for your Mac. Once you've installed the software for it, got to the System Preferences and click on Network. Under the list of network interfaces, click on the lock symbol, if locked, and provide the admin password. Next, click the "+" button and select your modem from the popup list. Next, provide the information on the right (phone number, username, password). Click on the "Advanced..." button for options related to the modem/dialing mode/volume/DNS/WINS/Proxies/PPP. Once provided, click "Connect" and the modem will dial and connect you.
If you aren't using RAS dialup, but are using the basic Windows VPN, the procedure is similar. At the network setup page, click the "+" symbol and select "VPN" from the popup list. Select the VPN type (whichever is being used by your office, L2TP or PPTP) and provide a thoughtful name for it (e.g., "Work VPN"). Once you click "OK", on the right you can specify the server address, account name, encryption type, and authentication settings. Clicking on the "Advanced..." button will bring up additional options, such as setting up VPN on-demand (connects whenever you attempt to access the specified domain). Your office may use certificates to authenticate, make sure that you have a copy of yours (provided by your IT group) ready.
If you are using Windows Remote Desktop, you may need to setup a VPN connection first (it depends on how your office is setup), as above. After that, you need to download an install [Microsoft's Remote Desktop Connection Client for Mac 2|http://download.microsoft.com/download/6/c/0/6c01c76e-fef9-4a59-9fe1-84b1a307 ad26/RDC200_ALL.dmg] from microsoft.com. After that's installed, simply start your VPN connection (if required) then double-click on the Remote Desktop Connection icon in the Applications folder. Provide your login information.
If you are using VPN software other than the basic Windows one at your office, you need to follow directions provided by the vendor.
If you are using something like Citrix, you'll need to download the Citrix client and follow the vendor's instructions on setting up the client.
If you are using a different remote access technology, refer to the documentation provided by the vendor or publicly available (such as SSH tunnel to a DMZ server).
