Click on an unoccupied room to carry out work on it: you can build new bedrooms, improve them, or install special rooms (restaurants, waste-disposals, ...).
Special rooms (restaurants, waste disposals, discos...) are used by clients who appreciate what they contain (food, smells, noise, ...): they earn you money for any time spent there. Example: a client who likes good food will go to the Restaurant often.
Note: Special rooms have no effect on neighboring rooms. This means that you can place a client who hates noise next door to a disco (yes, the insulation in these rooms is truly remarkable).
Expanding the hotel
Click on the Expand icon, located to the top left of your hotel. Then simply choose the location for the extension.