Project Requirements Help!

I just started work work placement with an IT company. My job over the coming months with be to automate many of their admin tasks. I've been asked as part of the Project Management Plan to put together the Project Requirements. However Im unsure what to do! I've tried googling sample requirements but havent found anything helpful.

So my question is; what is the process for putting together requirements? What is generally expected to be included and how into detail should I go?

Any advise/tips will be very much appreciated!