Document analysis is a key skill in historical interpretation. It is not a mere summary or description of what happened, but rather an analysis of the motivation, intent and purpose of a document within a particular historical context.
In this analysis you should:
(i) Explain what the document is (who produced it, for what purpose, who was the audience);
(ii) Place it in its historical context (why was it produced, to achieve what purpose);
(iii) Explain or comment upon specific important points, references and allusions in the text/illustration (show that you understand the setting of the document);
(iv) Comment upon ways in which the document might be used as an historical source.