When a program highlights a spelling or grammatical error, you can often right click on the underlined word to have a dictionary list of possible corrections pop-up. Simply scroll to and click on the correct spelling of the word, and the misspelled word in your document will be corrected.

For example, when I write 'ther' instead of 'there', a quick right-click lists the possible alternatives as 'three, there, her, the, and their'. For words that aren't in the program dictionary, you can choose to ignore all instances of the word or you can add it to the program dictionary.

The right click also works for grammatical errors, but here you have to be more careful. Computers aren't great at identifying grammatical errors, so it's advisable to assess the validity of grammar suggestions.