By now, you've put in a lot of time and effort to make sure that you are ready to hire the person who is the best possible fit for your program. Now it's just a matter of securing their services and notifying those you did not choose.
As an employer, the most important part of hiring is to make sure that you make an employment offer that is not, and cannot be confused for, an employment contract. You have to maintain the flexibility to let the person go, in the off chance that things don't go quite as well as you had hoped. We extend a verbal offer, then follow up with a formal offer letter that has to be signed and returned within a certain amount of time.
Once we receive the signed offer letter, we send rejection letters to applicants that were not offered positions. (One letter for those who interviewed with us and a different letter for those that were not granted interviews.) For those who were granted an interview, we assure them that we will keep their application on file for consideration for future openings.
Now it's time to start working with your new employee to help him or her to become a valuable member of your team.