Here is a copy of the SET(M) form so you can get an idea of the information and documents needed:
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/618245/set_m_-form-06-17.pdfGenerally speaking, the documents you needed to supply for your previous FLR(M) application will be the same needed for the SET(M) application. You'll need items such as evidence of living together the past two years, your passport and BRP, your spouse's passport, marriage certificate, evidence of accommodation and finances, and so on. (original or certified copies, as per usual)
You'll also need your pass certificate for the Knowledge of Life in the UK Test, so if you haven't already taken it, you'll need to get it done before you apply.