How to dispay custom field?

Question

I want to create custom field type is File Advanced in meta box

I read in web site https://docs.metabox.io/fields/file-advanced/

i have created field but i i don,t know how to write code right to display it

I have put a code in single.php

but there is a mistake

i am new guy honestly i don,t know how to code

please help me to write with coding

i read in in https://docs.metabox.io/fields/file-advanced/

but did not help me