Follow the steps for spell checking :
Click on 'Tools' in the menu bar and then 'Spelling and Grammar' from the drop-down menu, or press Alt + T and then press Alt + S, to open the 'Spelling' window.
Misspelled words will be highlighted with red colour. A number of suggestions will be available in the suggestion box. Choose the desired one and select Change/Change All/Auto Correct option as per the requirement and click on Close button to close the spelling dialogue box.
Documents can also be spell-checked any time by pressing F7.