Once an assessment integration is enabled for your organization, you'll be able to add the integration's assessment as an interview stage.
To add an interview stage to an existing job, navigate to your job (Jobs > Job Name) and click Job Setup.
Select Interview Plan on the left side of the page and click Add stage.
Scroll through the list and select the integration's stage on the next window.
When finished, click Add to apply the stage to the job's interview plan.
Once the stage is in the interview plan, you can modify it by selecting the pencil icon next to the stage name.
You can delete any stage by selecting the trash can icon.