New
#21
It's easy with a GUI: Minitool has Help, and articles on its site. There are videos on Youtube. Suggest you consider looking at these to gain confidence.
With Minitool, you basically slide things on the GUI. You can read the help - the program does come with help.
Drag and slide the left boundary of D to the right.
Drag and slide the right boundary of C to the right.
Click Apply
I think you've done it anyway.
Disk Imaging
Always best before making critical changes to make sure you have a current disk image before making the change.
Now you've made the change, consolidate things by creating a new base disk image. (E.g. Macrium reflect (free) )