You set Jira as the landing product on your site.

When Bob logs into the site for the first time, he will be redirected to the landing product, which is Jira. However, since he does not have product access to Jira, he will see a message that says “You don’t have access to this product” and a button that says “Request access”. If he clicks on the button, an access request will be generated for Jira, which will need to be approved by a product admin.

ReferencesSet your site’s landing product Request access to a product