1) Follow the link.
2) Select the "File" button in the left hand corner.
3) From the drop-down menu select "Copy spreadsheet."
4) Click "OK" on the Dialog Box.
This tool isn't just for Starting Strength trainees, but for anyone who wants an incremental warm-up for the Squat, Bench, Press, Deadlift, Powerclean and Row.
Sets 1-4 are to warm up, set 5 is the workset. In 'Starting Strength,' MR provides an example template of the warm-ups for each exercise and my calculator attempts to remain faithful to it. With all exercises (with the possible exception of the Deadlift) the first two sets are warmed-up with an empty barbell for 2 sets of 5, and the following 3 sets are incremental percentages of the workset (ie. 40%-60%-80%). You can rest as much or as little in between warm-up sets as you desire but I usually find the time it takes to swap out the weights is adequate.
The only exercise I took any liberties of my own with is the Deadlift. I lowered the warm-up sets/volume because 1) Those muscles were already warmed from the Squats 2) It became a lot of volume once you hit the heavier weights.
The warm-up is important not only to prepare the muscles for the impending maximal load, it's also to get some extra technique practice in. This becomes especially important with Squats, Deadlifts and Power Cleans, where technique deteriorates as weight increases.