Showing an awareness of the context of a text will demonstrate that you have a grounded understanding of the text, and this is sure to impresss examiners.
Firstly, it is important to rememeber that it is an English essay and not a History essay that you are writing. This means your entire focus should be on the text, and not some tangent about Henry the 8th or whatever it may be. Make sure the context is part of your analysis. Think about how it helps or changes your understanding of a text, and demonstrate this alongside evidence from the text itself. This means that your use of context is not a 'throw-away comment' at the end of a paragraph, but insightful analysis. It is important to remember it is not how much context you use, but how you use it!
Remember: English, not History.