it looks as if its mounted but not formatted yet.
Once you have formatted it that will then allow a drive letter assigned.
But......
Are you trying to turn it into your system disk using the current OS?
If so there should have been some software came with the drive to clone the system part of you disk over onto the SSD.
I have a Samsung and the software provided looked after everything for me.
Just plugged it in and told it what I wanted. Shut down swapped the disks about so I had the new boot disk where I wanted it and fired it up. Optimised it for max life span and haven't touched it since.