Microsoft Word should, by default, automatically spell check as you type. i.e. a squiggly red line should appear under any suspect words. If that's not happening, go to Tools > Options and click on the 'Spelling and Grammar' tab. Then click 'Options'. Click to ensure that there's a tick alongside 'Check spelling as I type' and click 'OK'.
When Microsoft Word finds a suspect word, it tries to work out what the user might have meant. For example, if I type 'chek', Word thinks that I might mean cheek, check, cheeky, cheeks or chic. Word can't decide what word to substitute; it's up to me to choose the correct option.
When you see a word underlined in red, right-click on it. You'll see a list of the options offered by Word. Click on the correct one to insert it.
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