SumDomain install

I saw another post similar to this one but was not clear on the resolution. I am also sure that this has been posted several times before but I did not find the answer during my search.

I have a hosted account with several domains.
aaa.com is the root directory and all other domains point to folders within the root.

For example, I have domain bbb.com that is under https://www.aaa.com/bbb.

I am trying to install wordpress into the bbb.com domain; however, when I try and navigate to bbb.com it won’t work and instead the wordpress installs as https://www.aaa.com/bbb

I do not want this to happen and I want it to look like there is no aaa there and only bbb.

How do I fix this? A redirect?
Basically I don’t want anyone knowing that bbb is a part of aaa.
Thank you for your help