Customizing Footer

I want to have a custom footer. I can edit on Facebook’s Production and insert the html properly. How can I insert it through wordpress by default so that it would automatically export to Facebook Production?

In footer, for example, I want to have “?Facebook dot come”. Right now, I have to manually insert to Facebook’s Production of my page on each article.
<footer><aside>?Facebook dot come</aside><footer>
Where in the plugin should I make the change so that the footer appears on every post through wordpress itself and I wouldn’t have to insert it manually on each post?

It would be a great help and will definitely give you a 5 star review if it works out and I know it will.

Thank you.