Please use Creative cloud desktop application to install Lightroom.
Click on the below link to download Creative cloud.
Once you have Lightroom installed, follow the steps provided in the below link to serialize Lightroom CC to Lightroom 6.
Let me know if this helps.
Thank you Mrinmay. I downloaded the CC version and when I tried to launch Lightroom I get the message "Cannot create the required folder: /Users/asta/Library/Application Support/Adobe/Lightroom/Develop Presets." and the startup screen appears to be frozen. Now what?