ODYSSEY Blue with Intel Celeron J4125 - 8GB RAM + 128GB SSD

I got this set today delivered by ANDRATEK.
I can see that the M.2 SATA SSD is installed in the M,2 slot. Windows 10 Enterprise is installed on this SSD.
But now I want to install a second SSD, a SSD M.2 NVME. To do this I have to open the blue case. But how can I open the case?
The next problem: How can I insert the “re_computer case: Stackable Middle Frame”? Even therefore I have to open the blue case.
Can anyone help me?
Many thanks!
Georg Holzknecht