Here is the video version, if you prefer it:
If you ever need to add a user to your computer (I had to once), then use adduser. It must be run as the superuser, so be sure to prefix it with sudo. (“How to Add and Delete Users on Ubuntu 18.04,” n.d.) Its usage is as follows:
adduser username
You can find more details in the reference above. A low-level alternative to adduser is useradd, but I had adduser available on the machine I was adding the user on (it had Debian 9 on it).
Hope you learned something new!
References
How to Add and Delete Users on Ubuntu 18.04. (n.d.). Retrieved February 10, 2020, from https://linuxize.com/post/how-to-add-and-delete-users-on-ubuntu-18-04/