Proxy_Pass usage example?

[unites]

Say I want to make a container behind the Nginx Proxy Manager (NPM) a page of another URL. Example would be have a django app at example.com/django while still having my static site container hosting example.com on a different container.

I tried putting this in the "Custom Nginx Configuration" but it seems to throw a 404.

location /django/ {
    proxy_pass http://insternal_app_host:30000/;
}

I am not really clear on what is allowed or not in the Custom Nginx Config. Are there any examples or further documentation on how to use it propperly?