Next, the Bottom Centers will be completed. This will require you to flip your cube upside down so that the semi-completed Orange side is facing down. When finished, all the Red Centers will be in place as shown. The corners are only displayed here for clarity; you will not have the corners completed at his time.

Bottom Centers

This step will work for all 4 of the Red Centers that you need to place. Simply repeat the steps below up to four times to complete the Bottom Centers. Your goals is top put a piece in the Top Back Left Corner of the cube, so you may need to spin the entire cube in your hands until you can provide an open slot in which to transfer the piece into.
Rotate your cube using  or  until you can position a Red Center in one of the 4 possible scenarios below. By following the moves next to the appropriate match, you will be able to correctly position that Red Center.

Now that you are finished with the Bottom Centers, proceed to the Bottom Corners.