. log in as an Administrator
. go to Admin -> under the Developer Tools Section -> Rename Modules:
However (this is a personal opinion): I do not recommend to rename existing modules for various reasons:
. the name may be hardcoded somewhere in the standard code
. the name may be hardcoded somewhere in some of the plugins
. the name appears in other labels which contain the name inside (but not referring to the module name label)
This will create a lot of confusion and if you do it by hand it may not be upgrade safe, or new (long labels) may appear with the original name of the renamed module.