Hello, I have an iMac 2011 21.5" and im trying to install my new Corsair RAM 8 Giga but im having issues with it. When im trying to install the Ram i dont hear any Click and if i just insert it the ram box barley closes. I did push them very hard! I was wondering , is there a need to first remove the ram i already have inside and then insert first the new ram and then the old one? If so how can i take out the old ram? Ive tried pushing out that black plug but it do nothing. Ease help me here! Thank you!