These days few of us have proper cellars so storing Port wine at home can be a problem. Don’t despair. All you need is a cool, dark, vibration free cupboard and a constant temperature, ideally no more than 15ºC (60ºF). Anything outside these parameters will see the wine age quickly and flatly. It basically becomes cooked and without life.
A Vintage Port bottle should rest on its side, with any visible splash of white paint uppermost. This keeps the cork moist at all times.
The ideal would be to have your Port stored professionally. Good wine merchants will undertake this and arrange for your wine to be insured for its steadily growing replacement value.