How do I upload a comments page to my template?

I created a WordPress blog to match my existing website. However, I just realized that I didn’t create a ‘comments.php’. The blog template has already been uploaded and running for a couple of months now. How can I get comments to work? I don’t see anywhere that I can upload a file to my existing template now.

If it helps, here is the link to my blog: http://www.mpower28.com/blog/

Thanks in advance for any help you can offer!