Would like to put content where category list is

Hi, everyone! I’ve had my blog for a couple of months now, and I’m pretty satisfied with its design, but I’d like to change it a little. On the right of the page is a column containing categories, archives, recent posts, etc. What I’d like to do is put some content in that area which explains the purpose of the blog, and also I’d like to put a small picture there. Here’s my blog as it is now: https://www.toonicornstudio.com

I have a link in the blog’s header called “About Toonicorn Studio”, but I’d rather have that info, plus the picture, in that right-hand area. Is there any way I can do this? Thanks for any help you can give me. ??