You have to figure out what type of learner you are - i.e. do you learn from writing something down, typing it out, saying it out loud etc. Usually, a combination of the three works best. If the essay is due next week let's say how about taking one paragraph a night. Read the paragraph, then try and say what you have just read out loud. Afterwards, try writing down what you have just learnt. Obviously there will be some spelling and grammar mistakes but by reading over and correcting your work you will be learning the essay at the same time. This takes time and practice especially with a language subject but it will get easier!