In Mac OS X/OS X/macOS and Other OS, There are three ways to install .ttf, .otf, .ttc, .dfont fonts:
A. Double click the file and click the "Install".
B. Open "Font" software under "Application" and choose the font you want to install.
C. Copy font file to "/Library/Fonts" and restart your computer. Early days, some software needs to copy the file to "/System/Library/Fonts".
Tip: Series of Mac OS X/OS X/macOS
Mac OS X series: Mac OS X 10.0(Cheetah), Mac OS X 10.1(Puma), Mac OS X 10.2(Jaguar), Mac OS X 10.3(Panther), Mac OS X 10.4(Tiger), Mac OS X 10.5(Leopard), Mac OS X 10.6(Snow Leopard), Mac OS X 10.7(Lion)
OS X series: OS X 10.8(Mountain Lion), OS X 10.9(Mavericks), OS X 10.10(Yosemite), OS X 10.11(El Capitan)
macOS series: macOS 10.12(Sierra)