Hmmm . If you want to make stairs walkable, go to doodads palette - bridges/ramps and fin invisible platform . Try to look my picture I attached below .
Place the invi platform into each steps .(the platforms is the checkerd object)
You can change the height of each platform by clicking this then press ctrl+Pageup, then If you want to make it lower , press ctrl+pagedown . (You can do this also in another doodads .)
Then in entering portal, you need to trigger it .
Place a region in a position of portal and another region that you want to become a destination, then do this following triggers . (look the attachment below)
The Enter Region is the entering point and the Exit Region is the destination point . You can place the destination point in any point that you want .