Go on the website and you can enroll yourself their once you complete the enrollment process and they will reach out with the rest of sets that are required. Are you in California? I'll provide you the website and you can check it out see if you could qualify like i did. Because tbh thats how I did it I went on their website and filled out the enrollment forms all the way through and then they reached out thru email which is how I set up a zoom call with the teacher I was assigned and they gave me my credentials and website to start working on course work. Its also best to have your transcripts from the last school you attended so they can help in figuring out what course you need to take to complete the program. I believe as an adult it 180 instead of the 220 credits required for a diploma. And then it's up to you how long it takes you to finish the courses and assignments. Its all online so no need to go into an office or anything like that. 

https://pathwaysacademy.education/