To change your careers site's URL, simply go to Company settings > Careers site.
Click Edit next to Address to pick a new subdomain for your careers site.
Click Save and your careers site's URL should be updated immediately. If people visit your old URL, they will be redirected to the new URL.
How can I ensure Google is indexing my careers site?
All Google - or any search engine - needs is to encounter a link to any page in your careers site.
Most teams link to their careers site from their marketing website. Google can index your entire careers site starting with that link.
While you can submit your URL to Google directly, you don’t need to — Google regularly crawls the web to add new websites to its index.