I am a designer and use a lot of different fonts. There are some pre installed fonts on the laptop and some options in software. I have more .ttf fonts and can I just place these in a folder? Or do I have to make a new folder and will it see them directly? There are many places where I find .ttf fonts.
Thanks in advance!
I believe you can place files in /usr/share/fonts for them to be automatically available.
Or use the Gnome Fonts tool that comes along with it. 
May have to update the font cache after dropping .ttf files in that directory (or subdirectory thereof).
Synaptic Package Manager has some fonts and certainly options in Debian or other distros have mechanisms for font installation. Whether True Type or Open Type Fonts (ttf or otf) both are readily installed in any Debian distro. Using mstcorefonts in Synaptic Package Manager will get you Microsoft Core fonts. Special sites such as https://help.accusoft.com/PrizmDoc/v12.1/HTML/Installing_Asian_Fonts_on_Ubuntu_and_Debian.html
are also available.
@taylor-williamc It appears that I do not have the rights to put new files there? I searched everywhere, but can not find where to log in to have the right rights?
Thanks for your quick reply!
Open a terminal and enter the following command
sudo cp some-font-file.ttf /usr/share/fonts
To keep it simple, initially have the .ttf files in your home directory.
As Kieran said, to move fonts there, you need to act as root by using sudo from the terminal. I think you can create a hidden directory under your home directory called .fonts (the . in front will automatically make it hidden) and then put font files in there. I haven’t tried this, but some documentation I’ve seen suggests that is another location that gets scanned for fonts. You wouldn’t need sudo for this and could even do it from the graphical file manager.
Alternatively, it seems like you might actually just be able to double-click the .ttf file to open it with GNOME Font Viewer, which then provides an option to install it. Again, haven’t tried that, but saw some documentation which suggested it.
@taylor-williamc Wow William, just tested the doubble click on the otf or ttf font and there is an option to install it. It works. That is easy!
Following the bread crumbs …
file:///usr/share/doc/fontconfig/fontconfig-user.html
(Forum software won’t allow a file: link, understandably.)
says go look in (among other places) /etc/fonts/fonts.conf for the config
and that says (in part)
<dir>/usr/share/fonts</dir>
<dir>/usr/X11R6/lib/X11/fonts</dir> <dir>/usr/local/share/fonts</dir>
<dir prefix="xdg">fonts</dir>
<!-- the following element will be removed in the future -->
<dir>~/.fonts</dir>
I don’t know how definite or how soon the “will be removed in the future” is.
@kieran Thanks for your help. I was succesful with the tip of taylor-williams. Just click the .ttf file and then the option appears to install it.
It will be eventually, use .local/share/fonts instead (user xdg). That follows structure of /usr/share/fonts (which is system xdg)
See https://wiki.archlinux.org/index.php/Font_configuration for details