The usual steps in installing a font :
1. Copy the ttf files to a directory
2. sudo mkfontscale - this generate an X11 font name for each of the fonts found in the directory. This info would be written into a fonts.scale file in the directory.
3. sudo mkfontdir - creates an index of X Font files in the directory and writes it into a fonts.dir file in the same directory.
4. sudo fc-cache -fv - this creates a font information caches for fontconfig systems. this enables application that uses fontconfig to load fonts more quickly.
But usually when adding new fonts, I just copy the fonts to ~/.fonts/ directory and run fc-cache -fv. These though would be available only for one user on the system.