Could someone guide me on how to play in the two player mode. When playing, in the upper right corner of the screen, it says push + to come in, but it is not active.

You have to set your remote to the wii.. In the screen before you load into the game you need to open up the wii and open up the second player wii remote and push and hold the red buttons at the same time. This will set that wii remote to the tv.. It should light up as two once this is done. OK now go into the game and you should be able to click plus on that remote and start it. Please let me know if this works so I can help further.

All you have to do is have both remotes synced, and have player two join in at any time your playing and press plus. I only know that this works for Wii, not sure about other consoles.