Footer is a second thing that you should develop when you building a new wp theme. It`s in footer.php file.
Footer should contain a severals widget areas, one to each column/row (it depends at the project - see Sample specification). Every option of footer (eg. numbers of cols, rows, post-footer)
must be placed in Customizer customizer. Remember to style every widget area properly. You should use monster widget to put every default Wordpress widget and style them to looks good in footer area.
Some things in footer could be placed from customizer opstions (eg. telephone numbers in complicated designs, copyrights) but when it is possible avoid that in favour of widegt area.
Similar to the header, when you placed the logo in the footer it should be linked to the main page. Second thing that you should check is moment when attached header image is not displayed - it should display page title.
You can use code below: