You have to do that through a custom theme. Maybe you already have one? If not, follow Manton’s instructions here. Then:
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Follow this link or go to Design → Edit Custom Themes.
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Click on your custom theme.
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Click on the template containing the
<head>section. Probablylayouts/partials/head.html. -
Add your
<link>element to the template.<link rel="me" href="https://example/yourhandle" /> -
Press Update Template, wait for your site to rebuild, and celebrate.
