Can you send emails at all?

If you can, all you need to do is attach the file of your assignment to an
email message.

If you can't send any emails, then it's a problem with your email
program/email account set up.  To get help with the former, better to post
your question to the appropriate newsgroup - it is not an issue with Word.
If the latter, as it seems that your email address is @yahoo.com, check with
yahoo.