You don't - MS Office is a totally separate & distinct suite of programs
unrelated to email software unless you're using Outlook. Your reference to
"MSN" makes it unclear as to what email software you're actually using, but
if it happens to be Windows Mail there is Spell Checking available in the
Tools menu. Some web mail programs also offer spell checkers - if that's
what you're using look into the Help/Support from that provider.