Once you have hired someone and would like to close the job, simply archive the job.
When you first log in, click on the 3 dot menu of the job opportunity and choose Archive.
Deactivating a job while reviewing candidates
If you are still evaluating candidates but no longer want to receive new candidates, simply deactivate the job application page.
Click on the settings wheel of your job opportunity, scroll to the bottom and select the option "deactivate the job application page" and save.