How can I get from Millennium Park to Navy Pier? PLEASE HELP!?

I'm going downtown tomorrow with some friends and I need the cheapest way to get from Millennium Park to Navy Pier. Either by walking (which is the cheapest lol), to which I definately dont know my way there:( which is where you all come in! Or by cab, but that's expensive , or by Bus? is there in busses? and where is the bus stop located? ive heard sumthing about a 124 bus, but idk, so PLEASE HELP ME OUT~!~