Really, if one will look at the http://www.kentico.com/cms-asp-net-features/Feature-Matrix.aspx to evaluate if Kentico CMS free edition is something that you can use for building a personal web site for your small non-profit organization, it will be clear that free edition contains only one blog. ok 1 blog will be enough for me, who cares, if our organization has only 10 people so let them use 1 common blog, that's all.
But, the truth is that Blog for the free edition comes without front-end editors for Blog. To post a blog message, you have to log in to CMSDesk (it is a content administration console) and add a new blog there.
I played with the blog page design trying to add a Edit Blog web part, but I got an error message saying that your license doesn't allow this.
Actual reason for this license limitation is that blog editing is implemented with the User contributions module (see Kentico developer's guide, Blog Module, On-site management via User contributions).
And, guess what, User contribution is not included neither in a Free edition nor in a profeccional one. So if you want to be your Blog a real blog, you will have to prepare 2K $ for an enterprise edition of Kentico. Or find another free blog engine for you .NET site (for example, subtext) :)