Candidates can reach a published job in three ways. Use whichever fits; you can use all of them.
The apply link
Every published job has its own apply link. Copy it from the checklist on the dashboard, or from the job page, and paste it in a job ad, LinkedIn post or email. It opens the job description and the application form.
The link only works while the job is published. Draft jobs aren't visible to anyone.
An Apply button for your careers site
On Jobs, copy the snippet under Add to your careers page and paste it before </body> on your site. It adds a floating Apply button that lists all your open jobs and runs the application and interview in a window on top of your page.
New jobs appear in the list as soon as you publish them. You don't need to change the snippet again.
A button on one job's page
Each job page has its own snippet. Any element with the data-apply-job attribute opens the application for that job. If the site-wide snippet is already on the page, you only need the button.
Not sure how to edit your careers site? Send the snippet to whoever manages it. It's one script tag, and works on most site builders that allow custom code.