If your web host has a control panel, most do, and most use cpanel. In the control panel there is a file manager. You host should have a doc page on how to use this file manager if they offer it.
They should also have the documentation on how to log into your site with FTP. This can differ from site to web host to web host so I can not give you specific directions. The best I can do is point you to some general WordPress documentation on how to:
- WordPress documentation covering FT access.
- Here’s basic tutorial Disable a WordPress Plugin Without Access to Your Admin Area
If you are not comfortable in doing this, open a support ticket with the web host asking them to delete the folder and paste a link to this support two threads you’ve open here. That way if they have a question, I can answer it. It would also be an ideal time to approach the subject of making sure your are running a current version of PHP.