could someone please tell me how to add a custom Monument, im wanting to use Custom Vending Machine but everything i try isnt working

Which step in the "How to set up custom monuments" section is going wrong for you?

Do you know if the monument marker name includes any <color> or <size> tags? You can probably tell this by whether the map marker is a non-standard color or size? If so, then you will need to include such tags inside the config, but it won't be obvious that you need to do so since they won't show up in the debug text. I'm planning to address that issue in a future update since.