The spellchecker in Microsoft Word is a great for weeding out those spelling errors that just seem to happen however hard you try to avoid them.
However the spelling tool is only as good as the list of words that Microsoft Word uses to compare your text against. So, your surname, the street you live in and your city will, likely as not, be reported as spelling errors even when spelled correctly. Luckily you can add your own words to the word list so that Word won’t report these as being spelling errors.
There are a couple of ways to add your own words to the word list and one is to type the word and let Word report it as being a spelling error. So, if you have spellcheck as you type turned on, any word that Word doesn’t recognize will have a red wriggly line underneath it.
If you see a red wriggly line under a word which is correctly spelled, right click the word and, click Add to Dictionary to add it to the list that Word compares your text against
If you press F7 or choose Review > Spelling & Grammar to spellcheck your document any spelling errors will appear in either a dialog on the screen or in a task pane on the right of the screen (depending on the version of Word you are using, Word 2013 is shown here, Word 2010 in the next step).
Check to ensure you have typed the word correctly and, if so, click Add to Dictionary (or Add) to add it to Word’s dictionary. In future Microsoft Word won’t report this word as being incorrectly spelled.