From the Tools menu, scroll down until you see the options for downloading and installing Write-N-Cite for MS Word or Google Docs.
This is how the MS Word menu should display with Write-N-Cite.
You will periodically need to "Sync My Database" so you have access to new citations that you've added to RefWorks.
For Mac users, it is better to use RefWorks' Write-N-Cite plugin for Google Docs.;
If you must use Write-N-Cite for MS Word for Mac, follow these instructions to download the proper version of the plugin for your operating system.: