You can prepare for the assessment by looking at our guide. ESA and UC Claims for Physical, Mental Health and Learning Difficulties: a guide to the limited capability for work assessment.
You will find questions you might be asked on page 125. - you can also read about medical evidence from page 113. - Medical evidence is normall submitted with the form - as you haven't done this, you need to make sure that you have photocopies so the assessor can take them away.