Import the $t() function from Svelte-intl-precompile

  import { t } from "svelte-intl-precompile";

Use it in javascript code:

  let string = $t("key-of-translation");

Or in Svelte code

<p>
  {$t("key-of-translation")}
</p>

Add config files in locales/...json manually or better use the i18n Ally extension

In the config of i18n Ally add the svelte framework and make sure it can find the locales folder.