If there is a misspelled word (:set spell to see what is misspelled), you
can navigate the cursor over that word and hit (from normal mode) z=. This
will open up a screen of possible corrections. The one you are most likely
looking for will be toward the top. Each possible spelling will have a
number next to it. Enter the number of the word you are looking for and hit
enter. The spelling of that word will have been updated.
Try misspelling something and give it a try yourself.
See :h z= for more details.
h/t Jake Worth