Running WP on a subdomain.

You can install WP anywhere you want.
Upload the files to the subdomain’s webspace, yes.
You have to assign a DB to your blog – and have the right info in the wp-config file. I don’t know of any method for “assigning a DB to the subdomain”. The DB comes with your hosting package (I assume) and the script(s) access it in the same way regardless where thjey are installed: in the root, in a subfolder or on a subdomain.

how about a scenario where you want 2 different WP websites, one on the root and the other on a subdomain?

example:
https://www.main-wp.com
and
https://www.main-wp.com/sub-wp/

do i need two versions of the DB installed?

i want to have the subdomain website to present a non english content of my main site.

appreciate any help.

Did you get an answer on this? I am trying to do the same thing. Actually, I want to use WP as CMS on my main site (domain.com), and also on a subdomain (subdomain.domain.com), but I want to use different themes. Do I need to load WP in both places? If yes, then I assume I must use 2 databases. If no, do I still create 2 databases?

Any help will be much appreciated. I’m not very tech-savvy.

You can run more than one WordPress installation with a single database. The Codex article, Installing Multiple Blogs has information on that as well as other tips that may apply to your situation.

WP didn’t work on one of my subdomains of good questions
But I’ve read some articles about it and also Installing Multiple Blogs that helped me with that. thanks