Not sure what you mean by "enable". The 6500 linecards are hot swappable so you can just insert the card into a spare slot in the chassis and it should be available to configure.
Are you having problems getting the switch to recognise the module ? If so it could be your IOS version.
The module is recognized in the sh Mod, but gets disable by an exception "PM_SCP-SP-1-LCP_FW_ERR: System resetting module 2 to recover from error: Linecard received system exception. Errcode =
You could try reseating the module but if it is recognised initially and there is enough power for it it looks like a hardware fault i'm afraid.