After you have signed up and logged in, you will be taken to the Character Roster page. You can also reach this page by clicking the 'Characters' link found in the main menu found on every page.
With a free trial account you will only be able to create one character. However, by upgrading, through subscribing or buying turns, you will gain the ability to create more characters as you progress through the game.
If you have room to create a character the 'Add Character' button will be enabled. Clicking that will take you Create Character page. The only information needed to create a character is