As for the publisher and page number, I can't say for sure since many societies have this book, I personally read the original excerpt in The Power of Thought.
This quote is an overview of Sartre's philosophy of action. Man is thrown into this absurd world and can only create his own essence through free choice and action, which is the connotation of the quote.
I am the barkeep of the Sartre Bar, if you still have any questions when writing your essay feel free to ask me to discuss them, good luck with your essay