I see a notification that Grammarly has been successfully installed

The notification indicates that you have already installed Grammarly for Windows and Mac. To continue using Grammarly, please log in: 

Windows

1. Find the Grammarly icon in the system tray (located in the lower-right corner of your screen), right-click on it, and choose Settings:
   
   
   

   Note: If you don't see the Grammarly icon in your system tray, please double-click the Grammarly thumbnail on your desktop or launch Grammarly in the Start menu.

2. Log in to your account​ by clicking Sign in and entering your login credentials.
   
3. Once you're logged in, the Grammarly floating widget will appear when you start typing. 

Find more information about Grammarly for Windows.

macOS

1. Find the Grammarly icon in the menu bar, which is located in the upper part of your screen, click on it, and choose Settings:
   
   
   

   Note: If you don't see the Grammarly icon in the menu bar, open Launchpad and select Grammarly Desktop. Alternatively, open Finder, select Applications, and double-click on Grammarly Desktop.

2. Log in to your account​ by clicking Sign in and entering your login credentials.
   
3. Once you're logged in, the Grammarly floating widget will appear when you start typing.  

Find more information about Grammarly for Mac.