Typing errors are highlighted in the document with a red underline. If you place the cursor over a word marked in this way, you can open the context menu to obtain a list of corrections. Select a correction to replace the word. If you make the same mistake again while editing the document, it will be marked as an error again.
To place the word pair in the AutoCorrect replacement table, open the AutoCorrect context menu and choose AutoCorrect. Make your selection from the submenu. The word is replaced and at the same time the word pair is placed in the replacement table.