Wordpress to APP using REST API

Hello Friends i have a wordpress site but i want to make an app connected to wordpress and show all my post in a listview.
After searching on google there are developer who tell that they use the REST API for WORDPRESS
So Anyone in NIOTRON have already made this kind of app?
Can i get a guide or aia file to help me?

i have already tested this but i face some issue. it shows only my 10 recent posts and also i want to show in list view the featured image of my wordpress post
Thanks for your help

yes i have read it but not working. when i try to add the 2nd code in function.php i have an error

You should post relevant screenshots to get better help.

ok il will try to add screenshots