Linux as a general rule doent have many true type fonts available pre installed either due to license restrictions or just because some think thats a windows thing ewwwww.
Fact of the matter its nice to have more options especially when you design or use graphical tools a lot.
First obtain the fonts you want. There are many sites out there for free fonts but some of the ones I go back to time and time again are:
Font Freak
1001 Free Fonts
GRSites
Once you have the ttf file that you want go into a terminal / console window
type ls ~/.fonts
If that comes up with a result showing no such file or directory we will need to create it with the command
mkdir ~/.fonts
Now go into the folder where your ttf files are located and copy them to the fonts folder by typing the command(s)
mv *.ttf ~/.fonts/
mv *.TTF ~/.fonts/
Some files may be lowercase some may be upper case the above two commands takes care of both of them
Now to finally be able to access them in a program you can reboot to refresh the font system or if you have access to the root password type in
sudo fc-cache -fv
You should now have access to them in abiword, gimp and all other programs
