hey..
so i've read a lot about this and i think this post would help you
http://eshop.macsales.com/installvideos/imac_27inch_late_2013/
http://eshop.macsales.com/installvideos/imac_21inch_late_2013/
the above websites show detailed videos, although the videos for ssd are not out yet.. they will be soon and i would advise you wait for them as they are your best bet
but if you cant wait , here are some other options
this method is not specific to your model but it should work as they are both late 2013 models
http://9to5mac.com/2015/02/13/how-to-swap-imac-hard-drive-for-ssd/
but personally i would advise you wait for the videos to come out if you plan on doing it yourself