Gparted is a GTK front-end to GNU Parted and an official GNOME partition-editing application. GParted is used for creating, deleting, resizing, moving, checking, and copying disk partitions and their file systems
If you are using a un allocated disk (in cause of virtual booting mostly) then you need to create a new partition table.
From Device Menu, Select Create New Partition Table
Partitions for rlxos installation
Primarily rlxos need only a single partition of atleast 10 GiB, for system to boot and work properly partitions should be atleast.
MBR on BIOS
Root partition for rlxos system image
GPT on BIOS
A atleast 1MiB partition for bios system with gpt scheme