First of all you need to have some form of disk manager software installed. This may be Suns Solstice Disksuite or Veritas Volume manager or any other Solaris supported utility.
Then you need to study the manuals and learn how to set up metadevices, how to attach them as mirrors etc.
Once you know which s/w you are going to use, and have a basic understanding of it, then please come back here for further advice if needed.