installation - Installing fonts for a specific program

I have to install the following fonts on Ubuntu for a program to run:

# Here starts the Tk part...
#my $qfont=$tl->X11Font('-*-new century schoolbook-medium-r-*--40-*-*-*-*-*-iso8859-1');
#my $qfont=$tl->X11Font('-monotype-arial-medium-r-*-*-50-*-*-*-*-*-iso8859-*');
my $qfont=$tl->X11Font('-*-freesans-medium-r-*-*-50-*-*-*-*-*-iso8859-*');
print "Question-Font:\n$qfont\n" if ($debug);

#my $tfont=$tl->X11Font('-*-helvetica-medium-r-*--30-*-*-*-*-*-iso8859-1');
#my $tfont=$tl->X11Font('-bitstream-*-medium-r-*-*-45-*-*-*-*-*-iso8859-1');
my $tfont=$tl->X11Font('-*-freesans-medium-r-*-*-40-*-*-*-*-*-iso8859-*');

print "Title-Font:\n$tfont\n" if($debug);

#my $sfont=$tl->X11Font('-*-freemono-medium-r-*-*-10-*-*-*-*-*-iso8859-*');
my $sfont=$tl->X11Font('-*-freesans-medium-r-*-*-20-*-*-*-*-*-iso8859-*');
print "Small-Font:\n$sfont\n" if($debug);

my $fixedfont=$tl->X11Font('-*-freemono-medium-r-*-*-*-*-*-*-*-*-iso8859-*');
print "Fixed-Font:\n$fixedfont\n" if($debug);

my $utf8font=$tl->X11Font('-*-freemono-medium-r-*-*-*-*-*-*-*-*-iso8859-*');

print "UTF8-Font:\n$utf8font\n" if($debug);

I extracted this from the program sourcecode. Could you please tell me how to install these fonts?