Mac Word 2011: Try the automatic installation by double-clicking wordfast.dot.
Then close Ms-Word and open it again before automatic installation can be done. If you see a 'Trusted sources' pane, check all options present in it. With versions of Ms-Word higher than Ms-Word 97, use Ms-Word's Tools > Macros > Security dialog box, set security to low.
2.2 If neither automatic, nor manual installation work.