Unable to send attachments from yahoo email MID7015

I am completely at a loss. Help! please!. I set up my yahoo email account ( or so I thought) and have been able to send and receive regular emails. However I tried to send a file that I had downloaded to office suite and the attachment came up with a red x. Now not at all sure what to do. Please anyone out there I would so appreciate your help. Thanks.

Thanks! I will give it a shot.