If you're full of patriotism, you're full of love for your country. Patriotism is associated with serving your country and waving the flag.
There are, actually, a lot of ways to demonstrate your patriotism. Waving the flag is an obvious way, but anything that celebrates your country or makes it stronger is a great display of patriotism. Whenever a country is at war, people are more vocal about their patriotism, playing patriotic songs and making speeches full of national pride. Showing patriotism is so important that politicians will argue with each other about who really has more patriotism.