Not a problem to access the install from the liveCD;
One needs to know what hard drive the system is installed to and what partition they want to access.
Do terminal command:
to see all partitions if using the legacy MBR partitioning scheme.
And "assuming" the installed system is on the first hard drive "sda"; then:
This mounts the 1st hard drive's 1st partition and gives you access.
sudo mkdir /mnt/work
sudo mount /dev/sda1 /mnt/work
Do whatever you need to do, and when done, ReMeMber to (UN)mount the device, else file system corruption - at some level - will result:
For instance, to list the files in your install's /home directory:
assuming the "username" you are using in the installed system is "medusa569".
ls -la /mnt/work/home/medusa569
sudo umount /mnt/work