If you can't find the Mendeley plugin in your MS Word, try these options below:
1. In Mendeley, check the 'Tools' menu whether or not you have installed the MS Word plug in. If not, you can install it and check again.
2. Check Word Add-ins. In Word, go to Files, select 'Options'. Choose the 'Add-ins' option on the left hand menu. Under 'Manage', choose Word Add-ins and select 'Go'.
In the Word Add-ins list, make sure you have the Mendeley add-ins checkbox selected.
Note: for Mac users, select 'Tools', and choose 'Add-ins'.
If you have already tried the options above, and still can't install the plugin, uninstall Mendeley Desktop and reinstall it usually fix the issue. Contact your Liaison Librarian if you need support.