Add disk to Virtual Machine

Firstly add the new disk via your virtualisation platform and reboot the VM.

Login to the VM and run fdisk -l and note down the new disk name (normally /dev/sdb if the VM only has one disk to begin with)

Run cfdisk /dev/sdb to create a new partition on the disk

Create ext4 partition

Run the mkfs.ext4 command against the new disk while specifying the partition number

mkfs.ext4 /dev/sdb1

Create mountpoint

Create a new mountpoint directory for the partition in the /mnt directory

mkdir /mnt/new-volume

Mount volume on mountpoint

mount /dev/sdb1 /mnt/new-volume

You can now browse your new volume at the created mountpoint

Make mountpoint persistent

To make the new mountpoint persist across reboots, modify the /etc/fstab file and add the following entry to the file

/dev/sdb1 /mnt/new-volume ext4 defaults 0 0