Register for noto|biotica by sending an email to firstname.lastname@example.org, with the subject "Please register me". Noto|biotica is open to anyone - but be aware that if you start posting and your posts are inappropriate, off-topic, or become a nuisance to the rest of the noto|biotica community, you will be unregistered with extreme prejudice and no recourse.
Once you're registered, feel free to start blogging - express an opinion, provide a perspective, whatever. The best place to start is to write a short profile blog about yourself - see others' profiles here to get an idea of content, style etc.
Posthaven, the blogging platform that supports noto|biotica, is really simple. Once registered, you can start adding posts straight away. Better still, you can post by email - simply send an email to email@example.com; the subject of your email will become the title of your post, the text of your email will appear as the post - and you've posted!