Yeah ! Thank you. In fact, I tried different ways. No, double-clic does not work. Nor open Inkscape from the dock. But simple click on Inkscape, than "open file" works ! And simple click an Inkscape-made-file, than "open with Inkscape", too. So, no problem yet. And thank you all....

Hi,
sadly I can't help you. I downloaded El Capitan last weekend - and Inkscape do not run yet.
I am in need of help like you, I wanted juste work on an image i began before
Thanks all for help !
Georges17