The qualifying period for ILR is 24 months living in UK as Spouse (this does not include any time under Fiancee Visa)
You can apply 28 days before reaching the end of the qualifying period.
Before applying for your ILR you will need to have a pass certificate for "Life in UK" test.
May I suggest that you start to review the requirements for ILR so that you can already begin preparations for some of the documentations that are required.
Take a look here for details of ILR application form and guidance notes
You can download the forms from the links at the upper right-hand side of the page.
Hope this helps
