You may install the fax printer driver on your work computer which will allow you to easily send a fax from any application. Just download the print driver and install it. When it asks for a phone number, enter the fax number you wish to send your faxes from and its PIN.
If you forgot the PIN, please contact your administrator. They can reset it by signing in to the Admin Control Panel and editing the WebFax which can be found under the Resources menu.