Word has a built-in spell check feature that you can use to check the spelling and grammar of your document. To get Word to automatically spell check your documents, open your document and go to File > Options. In the Options dialog box, click Proofing on the left menu. Look for the When Correcting Spelling and Grammar in Word option and make sure that the Check spelling as you type and Mark grammar errors as you type boxes are checked.
You also have the option to enable automatic spell checking as soon as you open a document. Go to File > Options and select the Advanced tab. Under the Editing Options section, check the box next to the option: Check spelling as you type.
Now when you open a document in Word, it will automatically spell check the document for you. You can also manually check the spelling and grammar at any time by going to the Review tab and clicking the Spelling & Grammar button.