First go through the registration process for the Guildwork part of the site, setup your username and password etc.
Here is how to attach yourself to the LS Website, you must already be a Member of the LS in-game for this to work though.
Login to your Guildwork account, at the top right corner, click on your Name -> Dashboard
Then click Characters -> Add Character to Guildwork
Enter Full Name, Game and Server, and click Proceed
A popup box will give you a code that you will have to add into your Lodestone Profile of your character in order to verify it's yours.
Goto the Lodestone site and login, then Profile -> Character Profile Settings
Edit your Biography and enter the code Guildwork gave you
Hit Preview -> Post to Save the code
Go back to Guildwork page and click "Add Character to Guildwork" on popup and your character will be added to the LS site automatically.
One of the Site Admins will have to adjust your membership group in order to see some parts of the site. So be sure to tell one of us when you added your character!