Welcome to Noder!
To connect to other posts, simply have their checkbox ticked as you submit your own post.
In the near future, we'll have three ways of organizing posts: new, popular, and original.
"New" simply means posts are ordered by the time they were posted - it's the default option.
"Popular" means posts are ordered by how many other posts have connected to them - in other words, posts at the top of the list have the most replies.
"Original" means only posts that didn't connect to any other posts are displayed - in other words, these are the posts which (in theory) start a new discussion.
Posts will be trimmed on an individual basis, after a set amount of time passes since the last direct reply, this amount to be decided later. Hence directly connecting to a post resets its deletion timer, like a 'bump' in a sense.