Error in locating ruby 3.3.8 and 'https://rubygems.org' in my folder

[marypoopies]

This is my first time posting on the community and please excuse for the inaccurate description of the issue.

I am a newbie to Ruby Rails and is working on a project the create an application on Github Codespace.

In order to set up the environment, I first try to:

(main) $ source 'https://rubygems.org'
ruby '3.3.8'
bash: https://rubygems.org: No such file or directory
ruby: No such file or directory -- 3.3.8 (LoadError)

Knowing that I have my Gemfile created can clearly defined the follow:

source "https://rubygems.org"

ruby "3.3.8"

gem "rails", "~> 7.1.5"

I also have installed the exact version of Ruby and turned it global. It would be much helpful if someone can point out where should I exactly look into.