Before you do anything I would advise you to create a backup of your site so that you could restore it if something goes wrong.

There is another way of doing this explained by Marion in her training where you can create a child theme using a plugin, you can try that but if it doesn't work for you (the plugin was not compatible with my theme), we will be using the same code in the footer without using a child theme.

I am using twenty twelve theme, so the code shown in the image that needs to be edited belongs to this specific them only, if you understand what to edit in your theme using this training then fine otherwise mention your theme(only free ones) and I will find it for you, but first I would advise you to try Marion's training because that's easier and only if it is not working for your theme, use this method.

You can check out Marion's training here.

Steps 1 - Go to the editor.