As larrabee mentioned, FLR(M) is almost practically the same as a fiance(e) visa. Instead of providing evidence of plans to marry, you need to provide evidence that you have married (your marriage certificate). If you can get proof of living together in the UK, that's something else to add, but if you've just moved over, gotten married, and are switching to FLR(M), even proof of cohabitation isn't really necessary since you will have only been here for a short time. Everything else is the same - details and evidence of adequate housing, your UK sponsor meeting the financial requirements, etc.
If you were able to get through the initial visa application without any issue, FLR(M) is essentially a repeat of that.
(you will need proof of cohabitation for the next FLR(M) two years down the line, so start saving those official mail items, and get your name on as many as possible... yes, be evil to those trees and do NOT go paperless)