If you did a workout, but had to scale it down, no worries. During the logging phase for any result, you'll be able to fully customize/modify your workout.
Start by going through the process of logging a result for a given workout. See Logging a result: the Whiteboard calendar and Logging a result: not on your Whiteboard calendar for details on how to log results.
From the log page you'll be able to modify each aspect of the workout, starting with the structure of the rounds and reps. Click on the default rep scheme to change it.
Next, modify the movements as needed. Click on any of the movements. From the overlay box that appears, change, add, or remove attributes. Click on the name of the movement in the overlay box to substitute a completely different movement.
Finally, be sure to click the "modified" button so as not to skew the Rx'd results. You'll also notice that as you adjust the workout above, the description below automatically gets updated with your version of the workout. In the example below, I've substituted pull-ups for ring rows and I've made the thruster 35#. The description reflects that.