Let's go "command line". Like I explained, it is easier to give clear
instructions that way. Here is how you can read the amount of main memory
(mainly the RAM but also the swap, i.e., an extension of the main memory onto
the disk, hence much slower) that is available and used:
$ free -h
Here is how you can read the space that is available and used in each of the
partitions of your disks:
$ df -h
Show us the outputs and we can explain them to you.
Like strypey explained you above, keyboard shortcuts to copy/paste from/to a
(virtual) terminal are different. You can use as well, the right click. Or
you can select the text to copy and use the middle click (simultaneous left
and right click if your mouse/touchpad only has two buttons) to paste.
As far as I understand you, the command you were given through IRC is "sudo
apt-get install trisquel-mini" and your system currently has both Trisquel's
default system and Trisquel Mini's base. Am I right?
When a new package ("trisquel-mini" above) is installed on Trisquel, it comes
in addition to what is already installed. When a package is updated, it
substitutes the previous version. You can have several desktop interfaces
(e.g., Trisquel's default, GNOME Shell and Trisquel Mini's) installed in a
same system. The one you want to use is to be chosen at the graphical login
screen, i.e., the screen where you click on your user name and input your
password. If you use Trisquel's or Trisquel's Mini default login screen, then
it is an icon at the right of your user name (after you click it) that allows
to choose a desktop interface.
So, you do not "have to" remove GNOME Shell. It does not eat up RAM if you do
not run it. Removing GNOME Shell would only save a few MB in the system
partition of your disk. It is not worth worrying about it. But you can remove
GNOME Shell if you really want to save a few MB. To do so, you can right
click on "gnome-shell" in the "Synaptic Package Manager", choose "Mark for
Removal", click on the "Apply" button and confirm. Or, in a terminal:
$ sudo apt-get remove gnome-shell