Select the task list you'd like to add. To add all tasks, click All Tasks.
Click the iCalendar button, located in the upper-right corner.
Copy the Events address URL by clicking the Copy link address command on the popup menu. Depending on your web browser, this command might be named Copy shortcut or Copy Link Location.
After copying the link, the address field at the top of the window should be automatically filled. If that doesn't happen, right-click the address field and select Paste from the popup menu, or press Ctrl+V.
The OK button will now be enabled. Click the OK button to add your Remember The Milk task list to PrintableCal's list of available calendar sources.