Thanks for posting! When you try to upload the excel file with your contacts what happens? Do you see any error messaging or does the page freeze or not load? Does the same thing happen if you try uploading the file as a .CSV? I'd appreciate any other details you can offer so that we can help troubleshoot this issue for you.
In regards to your second question- are you looking for a larger reach so that your promos are seen by more people than just the ones that you're sending to? If so, you should check out our Social Share feature. Social Share will allow you to share your campaigns to your social media accounts like Facebook, Twitter, and LinkedIn. So if you have followers or fans on any of those channels they can also see the promos that you're sending out via email. I hope that Social Share helps you get your promos to a larger audience!