Johnson Martin made me aware of this cool challenge. To participate, each user uploads their artworks via Instagram. You can check out the official dates in their calendar section. Make sure your letter or number is uploaded on the corresponding day. Don't forget the hashtags.
Here is an example to demonstrate. Let's say I made number 9 for this March . I will post it on the 28th of March "as stated on their calendar" with the following information:
Image Format: 1280x1280px
Hopefully that makes things clear, all you have to do is be creative and have some fun xD! Here are some of my favorites on twitter. Which one is your favorite? Let me know in the comment section below. I added captions so that you can choose :)!