Many fonts can be found as free downloads online.
After downloading the font file, open a finder window and navigate to the Downloads Folder.
Open a second Finder window and navigate to the Macintosh HD Folder > Library > Fonts.
At this point, go to the first Finder window with the Downloads Folder > Select the Font .zip file > Double Click .zip file to open > Click on the blue folder with the font title on it > click and drag the .ttf or .otf file into the second Finder window and place in the Fonts folder.
This font will now be available to use across all applications in your computer.