If you've followed DevDocs then you'll have _typography.less where you've defined your font by using .lib-font-face mixin. Now to use that font you can override @font-family-name__base variable by either declaring it in _themes.less file or in _variables.less files in your custom theme.
so you'll end up with something like
@font-family-name__base:'myfontname';
@font-family__base: @font-family-name__base, @font-family__sans-serif;
To add multiple fonts, firstly you'll add fonts by using .lib-font-face mixin inside _typography.less file multiple times as required:
.lib-font-face(
@family-name:'my-primary-font',
@font-path: '@{baseDir}fonts/path_to_file',
@font-weight: font_weight,
@font-style: font_style
);
.lib-font-face(
@family-name:'my-secondary-font',
@font-path: '@{baseDir}fonts/path_to_file',
@font-weight: font_weight,
@font-style: font_style
);
you can use these fonts by introducing new variables where required:
@font-family-name__base:'my-primary-font';
@font-family__base: @font-family-name__base, @font-family__sans-serif;
@font-family-name__secondary-font:'mysecondaryfontname';
@font-family__secondary: @font-family-name__secondary-font, @font-family__secondary-fallback-font;
Now @font-family__base and @font-family__secondary variables can be used where required in your css (less).
Note you only need to provide the path where all required font files are located without providing any extension, mixin will load all files for you.
Best Answer
The topic you referenced states:
You need to apply your theme after you create the theme's files.
Apply a theme
After you add your theme to the file system, you can apply it to your store. You apply a theme in Admin.
To apply a theme:
See this page for more information.