Download both the Mendeley Reference Manager and Mendeley Cite before you start.
In SciFinder-n, click on the downward arrow to save your citation:
In the dropdown menu, choose "Citation (.ris)":
Open the file you just saved, to change the file name, change where it is saved, etc. (Setting up a folder of files to pull into Mendeley all at once might be useful).
Next, open Mendeley Reference Manager. Click on Add new, and then "File(s) from computer."
Select your files, and they will be part of your Mendeley library, and available as citations in Word.
Setting ACS Citation Style
Open Word.
On the top bar, choose References, and the new Mendeley Cite button (on the far right):
Click on "Citation Settings" and then "Change Citation style."
Search for American Chemical Society. Choose it, and you're good to go!
How to Cite in Word:
Open Mendeley Cite tool, as explained directly above.
Search for and click on the appropriate Reference. Click the button at the bottom to insert the citation:
Adding your Bibliography:
Click on the three dots in Mendeley Cite, and choose Bibliography.