I purchased Lightroom 6 from b & H photo and now want to install it on my new laptop I am getting a message that j need to de installation on one of my computer how do I do this
Go to one of the computers where you installed Lightroom 6, launch Lightroom 6 on that computer and then Help->Sign Out.
You can only have two installations at the same time so it would seem that the two are used already.
Check under your Adobe ID to see them. Then you can deactivate one that you don't want