Open the Word document
Click the Review tab
Select Language
Click Set Proofing Language
Choose the correct language
Uncheck Do not check spelling or grammar
Click OK
To remove all red underlines, go to File
Click Options
Select Proofing
Uncheck Check spelling as you type
Uncheck Mark grammar errors as you type
Click OK
To remove a red underline from one word, right-click the word
Select Add to Dictionary
Or select Ignore All
To remove red underlines from a selected text, highlight the text
Go to Review
Click Language
Select Set Proofing Language
Choose the correct language for the selection
Click OK