I haven't had the chance to apply at ACS yet but based on the stories of some friends who work there, I will tell you how it's like. Aside from online applications, ACS also accepts walk in applicants. So if you want to go there directly, you can do so. Just bring in your resume and be at your best appearance.
Be prepared for a long wait. If you're a smoker, expect your craving to shoot up high here. First, give your resume to the receptionist. A member of the hr staff will then call your name after 30 minutes and you will be given a written examination. Don't worry, it's not that hard. It's just a bunch of questions that will test your grammar skills as well as your reading comprehension skills. If you pass, you will then be given a typing test with the hr lady directly looking at how fast you type.
Now, due to the high influx of applicants, it is most likely that you will be scheduled to come back for another day (that is in the event that you pass the typing test). The next time you come back, you will be given an english assesment exam. If you pass this, you will then be endorsed for the initial interview. I've been told that it usually takes hours in between for this to happen and is most likely to happen in just a single day so don't expect to have a job offer at the end of the day.
The next phase will be the final interview. Expect an American Executive to talk to you. If you pass this, there is still no guarantee that you will sign a contract. Some I heard have to come back a day or two for the job offer. and they weren't even scheduled. They just waited for the call or text of the hr people.
All I can say is it their hiring process may be long, but the wait is definitely worth it (that is if you get hired in a technical account). Customer Service Accounts are said to be much lower in terms of pay here, though.