Firstly, to remove your horse's handicap mark follow these steps
http://www.startersorders.com/phpBB2/vi ... php?t=3472
The horse files are then uploaded here:
http://www.sopl.info/sopl/tom10/main.php
But only when the season starts (later on this month) but you can register now.
Have a bash around that site above, it's quite easy to enter your horses when the races are up (you click Nominate, then the eligible horses will be displayed). All the initial races are maidens so enter them however you wish, depending on how your horses come out of that will dictate what path they follow for the season.