To Place a Building
To place a Building, drag it from the Building Tray on the Build Menu, and place it either on a neutral block or a block you already own.

To Move
Once a building is placed on the map, you can move it. To do so, simply tap and hold on the building. You will then enter Edit Mode. From there, select the Move option and you will be able to move the building around. Note that when you move a building to another block, there will be a cost to rebuild it.

You can also put a building back into your inventory when in Edit Mode.