Since you mention setting this up on your local machine, I assume this is a development environment, intended for your own testing (so the new user you are creating is still controlled by you on your machine rather than another person). If so, instead of emails being sent they will be displayed at http://localhost:3000/letter_opener (note the `http` rather than `https`).
> ![The confirm my account email showing on the letter_opener page](https://collab.codidact.org/uploads/j89g5gse9q5b06ysb2afturot7u8)
The relevant section of the installation guide is [Create administrator account](https://github.com/codidact/qpixel/blob/develop/INSTALLATION.md#create-administrator-account).
Note that when you click on "Confirm my account" in the letter_opener email page, you will get an error because the link is `https` and doesn't work in the development environment. I posted about this in ["Confirm my account" link shows as https in development](https://collab.codidact.org/posts/287795) and the quick fix is just to change `https` to `http` manually in the URL bar.
Your new user should then be confirmed. After the first time you sign in successfully as that new user, you will see them in the Users list (by clicking the "Users" button at the top left of each page).
> ![The Users button at the top left of the page](https://collab.codidact.org/uploads/yx61pieqkmbwzfkxoy2zc8nli59j)
You can then use your admin user to assign whatever abilities the new user should have.