"Do you just post in any section and designate the posting to fall into your Journal."
Yes. The journal entry will show how many replies it got - next to 'Discuss' (which takes you back to the post in its original thread) it says "3 comments", meaning 3 replies - including replies to replies etc.
"If I want to read the Journal of a fellow member now do I do it?"
If you're looking at a post by them, the first small icon by their name is a link to their journal:
If you want to find a person's journal without a post, try going to 'Options' at the top of all DU pages, and then click on 'User Profiles' on the left column. You get a 'search by username' box; type in the first few letters of their username, and you get a list of matches. If they have a journal, that same icon will appear by their name. Or type in your browser's URL box '
http://journals.democraticunderground.com/' followed by their DU username.
I think the idea was to allow a blog-like appearance for people to organise their posts into. Also, at one stage DU wasn't all indexed on Google etc., but the journal entries were, so adding 'good' posts to your journal was a way to get them seen on the internet. But all of DU is now indexed, as far as I know.