Delete old domains and add new one

Delete old domains and add new one

Hello, I am building my first website and bought two domains for it - didn't like first one, ditched it, bought second, don't like it, finally decided on the domain i want to use, but now I do not know how to fully delete the other two.
Seems like I am not allowed to have a third domain on a free account, but I don't even need three domains, how can I delete the other two, get a new one and only use the new one?

I am sorry for being so indecisive, but I wasn't aware that there's a limit :(

Any help would be highly appreciated, thank you!