The only way I know of to add a phone number is from your iPhone. If you've turned on iMessages on your iPhone, and you use the same Apple ID on your Mac, your phone number should show up in that send messages from pop up menu under accounts in Messages preferences.
Apart from this I'm not really sure what you can try. Check on your iPhone that iMessages are set to use your phone number. This can be done in Settings > Messages. Other than this, I guess try turning iMessages on your phone off and on again, or seeing an Apple Genious. Good luck! -- You received this message because you are subscribed to the Google Groups "MacVisionaries" group. To unsubscribe from this group and stop receiving emails from it, send an email to macvisionaries+unsubscr...@googlegroups.com. To post to this group, send email to macvisionaries@googlegroups.com. Visit this group at http://groups.google.com/group/macvisionaries?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
