If you have not already done so I would NOT recommend updating Lightroom CC 2015 to version 2 until Adobe have announced the next update.
The 2.0 and 2.1 versions have several problems that Adobe has acknowledged and are working to rectify the situation, e.g. the application requires a Force Quit to close.
If you have already updated and would like to ‘roll back’ the software to the previous version here is a link posted by Adobe: https://helpx.adobe.com/lightroom/kb/roll-back-to-prior-update.html
You may not need to implement step 3 unless you have a new camera that requires the 2015.1.1 / 6.1.1 version