I am just trying out Spriter so I am no expert.
That being said, I believe you have to save the spriter file on both formats (scml, scon), making sure first that you include the additional data for authoring tools (see photo)
.
After that, drag and drop the scml file inside your Construct 2 project and everything should be fine.
Also, check if you have the latest version of the Spriter Plugin https://dl.dropboxusercontent.com/u/257875422/temp/scml.rar and that it's correctly put inside your plugins folder.