Candlelight Processional is held in the theater by the American Pavillion. It is a massed choir, of area schools, with a WDW CM choir, an orchestra and celebrity narrator. The narrator reads the story of Christ..with the choirs singing appropriate music for each section.
Do you need to buy the CP pkg in order to see/hear this? No. You can line up in the standby line, well before the show. Or you can just stand outside the rear of the theater, and watch/listen from there.
If you decide to book a pkg, you choose from among three tiers of restaurants. When you eat at that restaurant, before the show, you will be given a pass. THen, about 40 mins before your show time, you head to the theater and get in the 'pkg' line. This group is allowed into the theater up to 20 mins before the start of the show (depending on which show it is), then about 5-8 mins before the show starts, those in the standby line are allowed in to find seats.
Ease of getting in, via the standby line, will depend on what show it is, day of the week, and the particular narrator for that show. Some shows are complelely full...others less so.
made in for the 2nd show. We actually sat 2nd row from the back. I will tell you that the show is definitely worth the wait BUT this year I'm doing the package! We had done the package the 2 years previous when it only used 1 TS credit off of our dining plan but when Disney changed it to 2 TS credits last year I decided NOPE not doing that. Really though I ended up paying one way or another - look at all the time I wasted 
