You just need to utilise one nested IF function if you have to write an IF statement with three outcomes. The first IF statement will handle the first possible outcome, while the second and third will be returned by the second and third IF statements, respectively. Note that if you have Office 365 installed, you can use the new IFS feature as well.
The Excel OR function returns TRUE if any of the supplied arguments is TRUE, and FALSE if all of the supplied arguments are FALSE. To test A1 for "x" or "y," for example, use =OR(A1="x",A1="y").