add affiliate link into footer of blog pages and post

I need a way to have add a footer link to 1 blog theme and all the childthemes. I want the link to say Powered by NAME OF MY PRODUCT. This link has to be a hyper link. I have to have some way in the settings of wordpress to click a button and give the end user the ability to have this turned on or off. In the consoloe of this plugin it would need to have a place they could add the clickbank id and it would add the id to the clickbank affiliate id that would be the hyer link for the footer. If you bid on this use the word golden. This job would need to be done in 24 hours. I will supply you with my theme and the link that they would been to use. they would enter there clickbank id and it would add it to my link for the footer