Fuse has built-in support for launching the importer within a modal. Simply pass the modal: true option when you instantiate your importer. 
const importerOptions = {
  modal: true 
};

const importer = new FuseImporter({ options: importerOptions });

importer.getSessionToken = ... // see https://fuse-docs.flatirons.com/getting-started/sessions

importer.show();
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