This is what i did, the same with Photoshop
C:\Windows\system32>cd C:\Program Files\CELSYS\CLIP STUDIO 1.5\CLIP STUDIO\
C:\Program Files\CELSYS\CLIP STUDIO 1.5\CLIP STUDIO>atloader.exe C:\Program Files\CELSYS\CLIP STUDIO 1.5\CLIP STUDIO\CLIPStudio.exe
Failed to create process: 0x2
C:\Program Files\CELSYS\CLIP STUDIO 1.5\CLIP STUDIO>
I pasted all the 3 files in x64 folder to program folder, both Ps and CSP