First things first, as long as you haven't registered, you cannot do anything but read. In the top right of your screen there is a link to the page where you can register.
If you have already registered, you need to login. If you are the only one using Geopoeia on the computer you are using now, you can select 'remember me'. Then you will always automatically log in when you visit the site.
Next: getting started...
What do you want to do?