First, we must create a new user. While still logged in as root, run adduser <username>, replacing <username> with your username (we will use hobnob as the username going forward). This will initiate a wizard that asks you for details about the user, and for you to enter a password. After this, a new user with the username hobnob will be created, with their own home directory located at /home/hobnob:

root@hobnob:# adduser hobnob
Adding user `hobnob' ...
Adding new group `hobnob' (1000) ...
Adding new user `hobnob' (1000) with group `hobnob' ...
Creating home directory `/home/hobnob' ...
Copying files from `/etc/skel' ...
Enter new UNIX password: <your-password>
Retype new UNIX password: <your-password>
passwd: password updated successfully
Changing the user information for hobnob
Enter the new value, or press ENTER for the default
  Full Name []: Daniel Li
  Room Number []: 
  Work Phone []: 
  Home Phone []: 
  Other []: 
Is the information correct? [Y/n] Y

Now that we have a user with reduced privileges, we can use it to execute everyday commands. Try logging in using a different terminal, with the username and password of your new user:

$ ssh hobnob@142.93.241.63
hobnob@142.93.241.63's password: <your-hobnob-user-password>
hobnob@hobnob:$ 

Great! We've created a user account with reduced privileges and are able to access the server with this new account. But because it has limited privileges, we won't be able to perform even simple administrative tasks. Try updating the package lists by running apt update; it will produce an error that says Permission denied because this action requires root privileges:

hobnob@hobnob:$ apt update
Reading package lists... Done
E: Could not open lock file /var/lib/apt/lists/lock - open (13: Permission denied)
E: Unable to lock directory /var/lib/apt/lists/
W: Problem unlinking the file /var/cache/apt/pkgcache.bin - RemoveCaches (13: Permission denied)
W: Problem unlinking the file /var/cache/apt/srcpkgcache.bin - RemoveCaches (13: Permission denied)

However, if we run the same command with our root user, it executes successfully:

root@hobnob:# apt update
Hit:1 https://repos.sonar.digitalocean.com/apt main InRelease
...
Hit:5 http://nyc2.mirrors.digitalocean.com/ubuntu bionic-backports InRelease
Reading package lists... Done
Building dependency tree 
Reading state information... Done