By working your way down the navigation tree structure, make sure the building you wish to open is visible in the navigation tree (see image below).
Place your cursor on the building you wish to open (see the first image below). When you do so, you get access to an icon called "Open" (see the second image below).
Click "Open" (see the first image below). When you do so, the building you are working with will open. When a building opens so does its building card (see the second image below). Via the building card you can work with a building. For more information on working with a building, see chapter 8 in the manual for Buildings. You will find it here.
