It took me a while to decipher, but I think you're talking about a Hollowtech II type crankset, and need to remove the plastic arm cap used to fit the non-drive crankarm onto the bb axle; there's a small finger-driven splined tool that's Shimano supplies with the crankset, the TL-FC 16, or you can get one of these from Park http://www.parktool.com/products/detail.asp?cat=25&item=BBT-9.