you do not need to go into crx de lite
create your schema
go the Forms and Documents
upload your schema
then create Adaptive Forms and select the uploaded schema from the form model tab
About themes - you can use out of the box themes and associate them with the form. if you need to create your own theme, you may make a copy of existing theme and paste it in a newly created folder and style the theme to your requirements
For AEM 6.2:
To create an adaptive form using an XML schema, you may refer to  & .
For creating theme, you may refer to .
Thanks for the reply, I thought the crxde lite was meant to be a developer's tool which means it should be possible to perform whatever task one is able to do on the Author on the crx de lite. So I guess my question then is, what should the crx de lite be used for?