So, every time I've go to update my project's blog, I have to spend a few minutes figuring out how to update it. Navigating my blog posts there's nothing to add a new post.
So, I'm mostly posting this for myself later:
to update your projects blog:
1. Go to my profile in top corner.
2. Do NOT click on blog, click on projects. (this is weird IMO).
3. Click your project.
4. Edit your project (to right of project's name text, click the tiny 3 stacked dots near heart and bookmark, then click edit)
5. Now on your projects page, click the blog tab (under the projects name, between “settings” and “files”).
6. Now click new post.
I'm probably just being dumb and missed something obvious. But this took me 10+ minutes to find this time (partly due to site loading very slow today). So now I will just reference this post.