The first secret can be reached in two ways: either go down the stairs to the first room to the right of the entryway. This room hold the big box that is filled with Pinky's... sorry, Demons. Turn sharp left. In the very corner, there is a lift.

Or, you can take the stairs down directly across from the entry, to the end room with the big lift and the yellow door. Here, you turn sharply to the right at the bottom of the stairs, and the lift will be in the corner.

The second secret is to the right, inside the blue door. There will be a welcome committee. Probably not with flowers.

And ending this level, we return to the regular show: E1M4 "Command Control".