First: Register with Comptia

Create an account then Schedule an in-person or online proctored exam.

I recommend an inperson at one of the local testing areas they will suggest.  Make this appointment now and then study until that date.  In other words don't wait to schedule as you will most likely procrastinate..

For online tests (at home).. 

Make sure you have a camera on your computer as well as a microphone since your will be proctored remotely.  Run a system test on your computer.

If testing from home.  On the exam day, clear your testing area put all your desk items outside your room. 

They have you take 4 pictures of your test area. Submit your Drivers License (student ID parent ID etc.).

When taking the test do not move your head outside the camera, do not take a drink of water, and do not look anywhere in the room, you must only look at your screen the entire time, or else they will talk to you through video or chat and possibly disqualify you.

After you pass it makes you take a survey. Then you will get your exam results. The passing score is 650.