When creating a job you can add a reward attached to the job ad. This means that if an employee within your company refers to a candidate who gets hired, he will be awarded the specified reward. This is an optional step under "Settings" while creating a new job.

After a reward is made on a job, in the "Share" tab the job is marked with a star.

Click on "Share job" and choose "Referral link", take a copy of the link and feel free to share.

When someone applies through the referral link the application is marked with a blue sourced tag

Open the application and scroll to the bottom of the page, under "Sourced by" there appears the employee name who shared the referral link.