You have to convince us that you really want this job, that it is your first option.
Do not say you apply becasue you studied IT–that would indicate a must, not a desire.
Oppositely, you should try to show some enthusiasm for the job, showing some passion for desktop support and for helping the others to solve problems.
Show us that you are looking forward to do this work, that you do not apply only becasue you need money.
I have always loved to troubleshoot computers. I am taking care of big LAN in my block. I read a lot about various software products, and I like to try new things. What is more, I enjoy talking to people and this job is one of the few IT positions that offers a lot of communication.
I meet the job requirements, as outlined in your job description. I believe to be a good match for this position and bring some value to your company. Most importantly, this is a kind of work I like to do, and I am sure I will enjoy doing it for a long time.