Once you have hired someone and would like to close the assessment, simply deactivate the assessment.
When you first log in, click on the assessment's 3 dot menu and choose "Deactivate".
Deactivating an assessment while reviewing candidates
If you are still evaluating candidates but no longer want to receive new candidates, disable candidate access to the welcome page.
Click on your assessment's three dot menu, and select "Settings". From there, choose the "Candidate Experience" tab and scroll down to the bottom of the page. You will then check the option to "Disable candidate access to application page" and save.