Hello, and welcome!

First of all, you should wait until you receive critique for lesson 1 before going on to the box challenge. Now would be a great time to tackle some drawing for the 50% rule, if you haven't started already.

Second, if you're going for official critique, then that should be handled within a few days by one of uncomfy's TAs. However, the way you've phrased the question makes it sound like you're going for unofficial critique, so I'll draft this answer based on that assumption. The Drawabox discord server has multiple different channels devoted to each specific lesson (lesson 1, lesson 2, etc.), but the only way for you to receive critique is through the Drawabox website. That being said, discord does give you the option to ask for feedback from the community while you are doing a lesson if you're ever confused by an exercise or want to know if you're going in the right direction. There is also an unofficial system for distributing community critique more equitably run via discord that might help you get critique sooner (though, again, community critique isn't guaranteed).

The community on discord is overall very welcoming for newcomers regardless of skill level and most people give genuine effort into giving feedback there, bearing in mind that full lesson critiques are handled exclusively over the Drawabox website. Whether you decide to make a discord account just for Drawabox is ultimately up to you, but I hope this answer helped clarify how feedback how feedback is handled on Drawabox's discord server.

If you're a paying user on the offical critique track, you must wait for critique before moving on to the next lesson, however a critique is guaranteed so there's no reason to request one on the discord.

If you're a free-tier user seeking community feedback, you should not wait for critique before moving on to the next lesson, because critiques are not guaranteed.

The discord is the appropriate place to request critiques for free-tier users; there is a channel in the discord called "critique-exchange" that has a pinned comment explaining the requirements for requesting community feedback on your submission. Read the whole thing and do what it says, but keep in mind that just because you submitted a request for critique, there is still no guarantee that you'll receive one in a timely manner - the only way to guarantee timely feedback is through the official critique track, available through the patreon.

I'm a free-tier user on lesson 6 right now and have only gotten community feedback up to lesson 3 (still waiting on feedback for my lesson 4 submission). That being said, the feedback I've gotten has been tremendously helpful in pointing out things I didn't notice about my work (as has the process of critiquing others' work), so it's definitely worth going through the critique exchange process even though feedback is not guaranteed.

Best of luck, have fun out there!