If you are talking about switching between patterns in general, the number pad to the left of the RedDrum sequencer is where the patterns are stored. Each number is capable of holding a pattern. Click on the number 1, create a pattern. Then click on number 2 create another pattern. Click run. Now if you click on the number 1 it plays the first pattern you created and if you click on 2 it creates the second pattern.
If you are talking about getting those patterns into the Reason Sequencer at the bottom so the pattern changes while your track plays, thats diffrent. In the Reason sequencer there are two guides, when says L and one says R. Put the L where you want the first pattern to start and the R where you want the first pattern to end. At the left of the sequencer are all of the tracks/instruments you are using, click on the RedDrum Go back up to the actual RedDrum. Have the first pattern selected. Then Right click on the reddrum and halfway down the pop up menu it should say copy pattern to track. This will copy the first pattern between the L and the R. Now repeat for the next pattern. Hope this helps
-Shwaz