Where do I add license keys?

I purchased two sets of old D2 and LoD CDS, when those games originally came out, many years ago. How do I add those 4 license keys to my Battle Net account?

So now I have 3 sets of D2 (6 license keys) as I recently purchased/downloaded D2 Classic and LOD from BNet. Both run fine on my Win 10 PC… now I’d like to use my other CD keys to play on another machine as well.