First, open the Customizer by going to Online Store > Themes and click on the green Customize button. Once inside, click on the Footer section. After clicking on it, you can see all the settings that pertain to the footer. From here you can change the background color, turn on/off social media icons, email signup, and more.
If you click back, you can see all the blocks listed under Footer. You can add, remove, reorganize as many blocks as you want. If you click on the block, you can see further settings.