Cristian,
The following steps should allow you to mount the other partitions:
*Open the Terminal Emulator app
*Type su and press enter. This should give you root access to the device.
*Change directory/folder to your data directory by typing: cd /data/media/0 and then press enter.
*Create a mount point directory for your "home" partition, type: mkdir home and then press enter (repeat as necessary for other partitions)
*Mount the partition by typing: mount -t ext4 /dev/block/sda4 /data/media/0/home and then press enter.
You will still run into file permission issues if you attempt to access the home folder without root. You will probably have to boot back into Linux and set broader permissions on the directories you want to access from android-x86.
Please let me know if you need further assistance.
Thanks,
Mark