1. Open your Word, the go to Preferences (command + ,)
2. Choose Spelling and Grammar on the left side bar
3. On the right, see the Custom Dictionary, choose the dictionary from the drop down list and click OK...
If there is no drop down list, proceed to step 4
4. Click Dictionaries on the right of the drop down list... New window will open
5. Tick "Custom Dictionaries" from the list, then click OK, and OK again to exit the Preferences. I
F no dictionary on the list, proceed to step 6
6. Click Add.. at the bottom and choose Custom Dictionary from the list (located at /user/[USER NAME]/Library/References/Microsoft)
7. Click Open
8. Then click OK, and OK again to exit the Preferences..
You should be good to go now...