Thank you for asking how to make a donation. This link should help:
To help with Krita in other ways, the very best thing to do is what you have already started, that is, getting involved on this forum.
Log in often and see if anyone has a question that you can answer. Share your artwork here. You can even participate in our monthly Art Challenge.
Sharing Krita-Artists posts on social media is another way to assist Krita.