Boot splash screen continuation of the process

[David.SM]

I found solution in https://forum.sparkylinux.org/index.php?topic=2563.0
I don't understand first part of process.
It says gksu gedit /etc/default/grub than edit the "quiet splash" to " ". Remove ---> quiet splash <--- without removing quotes. from the Linux command line

I where should I do this?

[nevertheless]

I where should I do this?

The instructions you quoted said from the command line. I feel like I am misunderstanding your question, but if you're new to linux maybe you don't know how to reach the command line? There should be a "Terminal" application somewhere in your start menu (it's hard to describe exactly what to look for because it depends on the desktop you're using.). The keyboard shortcut ALT-CTRL-t might open a terminal for you from the desktop.

What I would do is open the terminal and type sudo nano /etc/default/grub . Make my edits, then CTRL-w to save, CTRL-x to exit. (Instead of nano, I usually use "vi," but if you're new to Linux, that could be a big learning curve just to do one thing. Some distros come with featherpad or leafpad. You can start something like that instead of nano. You can look in your "Accessories" menu to see which editor you have. But, nano isn't bad.).