If someone else has taken your content without asking, here's what you can do:

Reach Out:

Contact the person in charge of the website that copied your content. Tell them you own the content and ask them nicely to remove it.

Use Legal Means:

If they don't answer, you can send them a DMCA notice. This is a legal document that usually makes them take the content down.

Protect Your Content:

Put self-referential canonical tags on your website's content. This helps search engines understand that your content is the original.