php - access variables so I can display them in a twig file -

i totally new twig. far looks great , want learn better. understand syntax far don't understand declare variables or global variables can use them in twig file. downloaded wordpress template contains twig files , trying edit single.twig file access values advanced custom field group specifically. don't have symfony or timber yet. i'm confused controller or environment loader located . can me or link me free basic tutorial how variables twig file can @ least display them? hope question not vague. thank @ all.

it hard without real code example, @ twig documentation. somewhere in code has call render() function, can pass variables

$twig->render('index.html', array('the' => 'variables', 'go' => 'here'));