Well, create/format a new partition with file system ext4, you can use GParted to do that. Open a terminal and paste this command to install it: sudo apt-get install gparted
Search on Google how to create/format partitions with GParted.
Download the DarkMatter 4.7 ISO file and extract it into the new partition that you just created.
In this case you just need to extract the following files: system.sfs initrd.img ramdisk.img gearlock kernel findme and make a folder named data inside that partition too.
Now, make the GRUB menu show when you turn on your computer, to let you choose which operating system you want to boot.
Paste this in a terminal and hit Enter: sudoedit /etc/default/grub
Find "GRUB_TIMEOUT=" and change the value to whatever you want, like 3 or 5.
Change GRUB_TIMEOUT_STYLE="hidden" to GRUB_TIMEOUT_STYLE="menu"
Save pressing Ctrl+s and close pressing Ctrl+x
Now, in the terminal execute: sudoedit /etc/grub.d/40_custom
Copy the code below and paste it on the bottom of /etc/grub.d/40_custom
️ WARNING: On set root='(hd0,7)' youhave to change the number 7 for the number of the partition you created for DarkMatter, in my case is sda7.
To find out that number just execute in a terminal: lsblk
Grab the number after sda
Finally execute this command in a terminal: sudo update-grub