Grammarly

Step 1: Follow prompts to setup an account.

Step 2: Grammarly can check your Google Docs as you type, BUT it works better when you copy and paste your text into it directly. Click on the Grammarly icon and select "New document"

Step 3: This will open a new tab and give you a location to paste your copied text.

Step 4: Click on the underlined words or phrases to make corrections.

Step 5: Copy and paste the corrected text back into the Google Doc.