Hi, and welcome!
The sign-in button only appears if you are not already signed in. In its place, if you are signed in, the Log-out button appears (upper right on the page). Most members use the default setting, which is to remain signed in automatically when on their regular computer, so that they don’t have to keep signing on every time they look at the forum. If you use a different computer or log out of the forum, then you’ll need to sign in again.
The blog is Rose’s blog and is dedicated to her writing and articles, so there is no option for others to post new threads there, only comments to the articles she posts. The forum is designed for the community to interact amongst themselves. Rose rarely if ever participates in the forums. There you can post new threads.
To post a question directly to Woody/ Rose, use the “Ask Your Questions” thread over on the blog. To ask a question of the baking community on the forums, post a new thread (or comment on an existing one) under one of the subject areas.
Hope that clears things up!