How to connect a single font for the whole website?

The original headers had a single font, different paragraphs, etc. About 3-4 fonts. Decided to make one font for the whole site use this code
<style>
 @font-face {
 font-family: 'AppleGaramond-Light'; 
 src: url(fonts/AppleGaramond.ttf); 
}
</style>
Nothing happens. I need the whole site to sort out , changing the old font on this , everywhere to do the same? or is there another way
July 2nd 19 at 18:03
1 answer
July 2nd 19 at 18:05
body {

}

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