I tried this on plain all-white multiplait without any instructions thinking it couldn't be that much different from three-strand and after several goes finally managed a reasonably acceptable splice (I'm confident it will hold fine, just not quite as pretty as it might be).
Later found the Jimmy Green website - see http://www.jimmygreen.co.uk/technical_info/anchorplait_splicing_guide.htm
which gives instructions, and if you don't have pre-marked strand stuff as they sell, I'd strongly recommend marking the strands with a felt tip before starting - it can get confusing.
You will need a good set of splicing tools, the plastic one will do if you don't do much but the metal ones are much better. Also spaying them with some sail slide lube make the job easier