WordPress doesn’t include ads of any kind, so there’s no standard process for removing them.
Possible reasons you could be seeing ads are:
- Your host is adding them, possibly as a condition of a cheap/free hosting plan.
- You installed a pirated theme or plugin that contains malicious code.
- Your website has been hacked in some other way. This seems unlikely if you saw them right after installing.
- You have been hacked, and you have malware on your computer that’s displaying ads on web pages.
- Your ISP is injecting them.
This site is not an appropriate place for resolving any of those issues, so my suggestion would be to start by speaking to your host.