Relations between tables

[Wemago]

I'm playing a bit with this system and loved it. Tried to install D6 but unsuccessful and I saw the code and I'm not a lover of that type of use of js and I love the simplicity of D5 with php.

Now, I've created a blog table on MySQL, where there is a author_id column, and I'm using settings to make relation of author id with user id, the problem is, how do you set it to get real id of the author ( which is the one is creating it ) without using dropdown. That should be automatically set when creating the post.

Thanks