Need help making a theme for my site

Hi there,

I own the website bigvideogamereviewer.com. I have a problem where I already have a theme uploaded for my website. But before people can actually go to my website, I would like to have people make a small, one-time payment fee to access my website. The one time payment fee page would come up asking for the user name and password for those who have already paied for the site and can login to the normal site. Those who can’t should register and make a payment to the site. I would also offer a free page that everyone can look into that offers free items such as a free video or sweepstakes so that everyone can still benefit from the website. Also, the template that I currently have up right now does not have a place for me to upload an affiliate banner for my site. Can I upload one of those without having to actually change my website, or do I have to make my own website for that? Sorry for the lengthy paragraph, but if you can help me out that would be a great deal of help for me.