There is no way to attach documents to a communication at the moment. This is an oversight, and is on the roadmap for future functionality. In the meantime, there are three possible ways around the problem. The third way is the one that is probably best:
1) Convert whatever it is you want to send into HTML (if it's a word document there is a "Save as HTML" option under the file/save menu in word). Then you can click "Source" on the email toolbar, copy and paste the html into the text area, then click Source again, and the document should be formatted properly.
OR
2) Upload whatever it is that you want to send to a server somewhere (via whatever method you use to maintain your website) and then send an email to everyone with a LINK to that file within the email.
OR
3) Select whatever criteria you want to use to send the email as per usual (ie select all your leagues/teams etc). Then go to the next step. Type any old thing into the subject and body text and click next. On the last step you will see a LIST of all the people/email addresses that the system is going to send to. You can then copy and paste this list out of the web browser and into excel, and then copy and paste all the email addresses out of excel and into your usual email sending program (outlook I would guess). Then you can attach and send as usual. NOTE: If you use this method, BE SURE TO PUT THE EMAIL ADDRESSES IN THE BCC Field, and not the TO field - otherwise if someone accidentally clicks "Reply to all" they will send an email to everyone on the list.