If you're unsure what is CLI you can read about it <here>. Meanwhile you need to have a look what's around you on the CLI and for that you use the ls CLI command. To see the full capabilities of the beforementioned command you can use the man (stands for manual) command.
vella@vella:~$ man ls ... ... the magic will happen here ... vella@vella:~$
Personally I like to use ls -l variations of the above command but that's where my laziness kicks in and instead of writing out 4 characters and 1 space (5 key strokes) you can create an alias for yourself and bring this down to just 2 key strokes. Lots of Linux distros have this alias already predefined somewhere in /home/<user>/.bashrc and it just needs to be uncommented to start using it. If it's not there then you need to define it yourself in that file or just on CLI. The difference here is that using .bashrc will make this permanent while doing it on CLI will only last during you running CLI session. The below are my two alieases for ls where ll is the short version of ls -l and ls alone will do listing in nice colors.
vella@vella:~$ alias | grep ls alias ll='ls -l' alias ls='ls --color=auto' vella@vella:~$
And finally, this is how you list any files or directories under Desktop
vella@vella:~$ ll Desktop/ total 1644 -rw-r--r-- 1 vella vella 77602 Jun 19 19:51 gcp_error.png -rw-r--r-- 1 vella vella 1605398 Jun 20 21:49 roses.png vella@vella:~$