The newsletter now requires use of the UserDefinedForms Module (the abillity to create / edit forms in the CMS). Download that module, install it and you should be able to create your subscription form
I now have the newsletter module and userforms running in 2.3.0 - but when i submit the subscription page i get the conformance but the new subscriber is not inserted into the database. Whats going wrong here?
When you have installed the "User defined forms"-module you can create a page type "Subscribe Form".
This form lets your subscribers fill out the form and on submit are added to your newsletters mailling list.
You can read about custom subscribe forms at http://doc.silverstripe.org/doku.php?id=recipes:forms
or just modify the subscribe form comming with the newletter module in the php file "newsletter\code\SubscribeForm.php"