Hi Sarah
I would recommend 3 things.
1- Talk to your supervisor, s/he should be able to give you advice based on your topic, discipine & faculty regulations/requirements.
2 - Before doing this, locate a copy of your school's 'Thesis/Dissertation' requirements document. This should be readily available online - if you can't find it, call the graduate office.
3 - If you are stuck at this point, investing in a good 'how-to' manual might be a good way to go. There are many excellent ones - I am sure your library will have a selection. I would personally recommend 'Destination Dissertation' as a good place to start, especially if you are in the lit review/early stages. If you do a search for 'Destination Dissertation' at Amazon, you will also get a bunch of other titles that may speak to you more.
Good luck