Before attempting a back carry with a ssc you need to be sure that your baby has good trunk control – they should be able to sit unaided for an extended period of time.  If you are wanting to do back carries and your baby is not yet sitting then an alternative is a mei tai or a woven wrap.  When attempting a back carry for the first time it is a good idea to have someone available to use as a spotter, or practice over a soft surface like a bed,

This video shows a few different techniques for how to get baby onto your back for a back carry with a ssc