The structure you are working with seems to relate well here. You would have to start with a users table that had at least one record, this user would then need to have a record in the blogs table with their user id. Once you have the tables with at least one record for these you can insert into the blog items table the current blog entry from the user.
This page should just be inserting into your blog entries table after the user logs in and selects the blog or has the blog set automatically based on their id.
If you would like the page to be doing more than the single insert you can just add to it with more insert server behaviors. I think it would be best for you to get the page working with the main insert on it first though. Please post back with any additional questions you have about any part of this.