Hi,
The Xo Material theme requires ACF Pro in order to use certain options. The Footer settings are provided in the WP Admin → Theme Options → Footer. Note that the ACF plugin is only required for the theme and not required by the Xo for Angular plugin itself.
Example below of the setting used on my own site: https://angularxo.io
Feel free to open issues for either the Xo for Angular plugin or the Xo Material theme on Github.