As I mentioned in Power BI first impressions, Power BI Q&A is an instantaneous search experience that uses a natural language query.  The user enters a question and it interprets it and serves up the correct interactive chart or graph.  It only worked with sample data installed when you create the Power BI sites, until now.  Now you can preview Q&A with your own data.  Adding your models to Q&A is easy:

1. Upload your workbook to your Power BI Site by clicking on the add link and selecting “Upload file”
2. This will upload and enable your workbook for use in the Power BI site.  After your workbook has been enabled, click on the three dots on the thumbnail for your workbook and select “Add to Q&A”
3. One you’ve completed these steps you can navigate to the Q&A question by clicking the “Search with Power BI Q&A” link in the upper right hand corner of your Power BI site

More info:

Live Now! Q&A with your Data

Power BI Q&A Preview Now Live On Your Data

Power BI Forum

Power BI Review, Part 2.5: Q&A (Now I’ve Used It With My Data)