Let's explore these one at a time.
You can get to the QUBES blog from any page by going to Community -> Blog from the top-most menu system, or you can use the URL https://qubeshub.org/blog. This blog space, as mentioned in the Hello World post, will be used to give QUBES project updates, news, and highlights, as well as general topics of interest to this community.
Every group on the Hub can have a blog, which can be activated in that group's settings. An example can be seen in the group QUBES Support Group: Building Community. Once on the group overview page, you will see a link to the Blog section in the left panel:
If you are a registered user of QUBES, you already have your own blogging space. To access it, first go to your Dashboard (to get to your Dashboard, click the profile icon in the upper right corner).
Once on your Dashboard, you will see the Blog section in the left panel: