You will find in folder <rhapsodyInstallationDirectory>\Sodius\RulesComposer\help\tutorial1
documentation to customize Xmi Toolkits:
XmiForRhapsody - Importing Rules_Tutorial.pdf
Tau - Importing Rules_Tutorial.pdf
Statemate - Importing Rules_Tutorial.pdf
1) Where <rhapsodyInstallationDirectory> is for example: C:\Program Files\IBM\Rational\Rhapsody\7.5.1