A better way to get there is jumping across from the upstairs corridor with the offices back towards the main lobby, there's a small tunnel. Throw a chair there and keep it up in the shaft. Drop down to the fenced off area, pull one switch, and then pull a second hidden switch that's near a wall. Then go back, jump across, you'll find the first secret room unlocked, and you can use the chair to climb up and walk across the crane to get to the second, teddy bear poker secret room.

You can find a side room with some boxes and barrels to your left. Stack them up on top of one of the crates to get to the vent. https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=3337850550
Hope that helps.

okay but like, how do you get up there?