procedures and direct links on how to use gpio's 

ref1: https://libre.computer/2018/05/19/gpio-headers-reference-for-aml-s905x-cc/

ref2: https://www.facebook.com/groups/356363581444452/permalink/439983209749155/

user "is there an app that you have to use in order to program to the i/o pins?"
even though there are links in ref1 it would be useful to have procedures and direct links on how to use gpio's 