Please take a look at this KB article:
"After you connect, log into the LEM appliance to make changes or view data. The user account for these functions is cmc and you set the password after activating your LEM license. If you are evaluating LEM, the default password is password."
If it's been changed, you can still access the CMC shell from the virtual console (VMWare or HyperV) or by physically accessing the box, and there is a PASSWORD command under the APPLIANCE menu. However, you'll need to old password to change it. If that's completely lost to the ether, you can call support and we can use the root account to get in and reset the CMC user for you.