There are some instructions on using the migration tool at the bottom of this blog post:
The tool is quite good, but I have found it to be buggy with pivot charts (I tend to unlink and fix pivots and then delete the master items). The other downside is that it can bring across lots of stuff that is useful in QlikView but not so much in Sense. In some cases I will migrate an app and then create a new app alongside it and copy and paste just the bits I want across.
Hope that helps.