Hi,
By custom footer, I guess you are referring to the footer text information. Currently, there is no such feature within the theme. For this, you can open the footer.php file within the theme folder and make the changes there. However, you will need to redo the changes whenever you update the theme as your changes will be lost while updating the theme. So, please make the changes via child theme https://codex.wordpress.org/Child_Themes.
We would really appreciate it if you could put our credit link in the footer as this is a benefit that we get from giving a free theme. Thanks.
