Once you meet the qualifications, you are likely to be notified that you are "on call" for jury service. The court will let you know how to keep in touch by using the call-in system used by potential jurors to check in each evening to see if they will be needed the following day.
You will need to let your employer know when you are "on-call" for jury service. Do not take time off from work or school until you have actually been instructed to come to the courthouse. The court cannot issue a letter stating you have been served on a jury if you were never called.