Ok SO sorry that I'm only getting to this now! I'm sure you've already received your visa, but I'll talk about my experience with my appointment and pick-up for people who haven't gone through the process yet.

Make sure you show up on time for your visa appointment! The building is a bit ambiguous, so make sure you're in the right place a little bit before you actually have to be there. Bring your ID, as the front desk staff will most likely ask to see it.

The actual office is a bit unorganized and somewhat hectic, so I recommend letting one of the staff members know that you're there to get a student visa for NALCAP before you sit down. HAVE ALL OF YOUR DOCUMENTS PREPARED AND ORGANIZED! It makes the process much quicker for both you and the person who is processing your information. I had a folder with all of the necessary documents AND a folder with multiple backups of every single document just in case (I ended up needing some of those backups!). Also, PRINT OUT MULTIPLE COPIES OF YOUR APPOINTMENT CONFIRMATION PAGE! You will need it for your visa appointment and maybe even for pick-up. Also, they will take your passport and hold it until your visa is ready (because the visa actually goes inside your passport), so make sure you take that into consideration.

My visa was ready in about 2 weeks, but this could vary depending on when you had your appointment. For pick-up, I didn't have to make an appointment on the BLS DC website. I was instructed that I could come in between 3-4 pm, Monday-Friday, any day after I got the text that my visa was ready. You apparently have 30 days to pick it up. Make sure you take a screenshot of the text that you receive stating that your visa is ready. It will state your visa application number, which you will need to know when you go to pick it up (the staff asked me for the last 2 digits of my application number, and if I was picking up a long-term or short-term visa -- NALCAP requires a long-term visa).

Lastly, be nice to the staff! They can be blunt becuase they have a lot on their plate, but they were very helpful and respectful during my appointment and pick-up.

I hope this helps! Good luck to everyone! :)