I set up my own Virtual Machine and what you need is an instance of SQL Server 2016 or SQL Server vNext CTP v1.1. Also install Analysis Services Tabular or Multi-dimensional mode and sample database for the same.
Note: The preview version supports only Power BI Dashboards connected to Analysis Services on-premises otherwise you will get the following error.
Download the January 2017 Technical Preview
It comprises of 3 files
Note: You will be seeing Create Database button in the screenshot similar to the above instead of Change Database. The above screenshot was taken once the Database was created.
Install the Power BI Desktop for Reporting Services 64-bit version and create a Power BI Report connected to your Analysis Services Database. Upload your new Power BI Report created using the Preview version of Power BI Desktop to the SSRS Portal and try navigating to the report.
As you can see from the above screenshot, Power BI report opens within the SSRS Portal Browser window.
I am really looking forward for the public release of this functionality.