1. Log in to Kraken.
2. Click on the XBT/EUR pair (or whichever you have) on the top left side of the screen.
3. Scroll down on the dropdown menu till you see XMR.
4. Click on XMR/EUR pair.
5. Now click on "New Order" and sell your XMR for EUR. "New Order" is located under the "Funding" menu on the main page.

NOTE: Make sure to click on the "Sell" bar when you want to sell your XMR. It's initially set on "Buy" by default.

OK, I've added 2 pics to show you how to do it. Let me know if you managed to do it.

http://imgur.com/a/lPg1K
http://imgur.com/a/dKDrO