How to mount/format/use eMMC module space to store files

Hi guys! My RPi is the v1.3 and is booting from nvme m.2 drive. The eMMC module is installed, but is not mounted on my raspbian OS. I tryed some ways but no success. lsblk command shows it as mmcblk1. I want to use the space to store files. Any idea?

Is this a trick question?
Create one or more partitions, format it/them, mount it/them.

No it isn’t. I tryed to use the command mount in many ways but it didn’t work. It has 16Gb and is not been used at all.

Did you create a partition table?
Did you create any partitions?
Did you format any partitions that you created?

No, I really don’t know how to do that…

fdisk /dev/mmcblk1 and follow the menus to create or modify partition table.
mkfs.ext4 /dev/mmcblk1pX to format the partition.
mount /dev/mmcblk1pX /mnt/whatever to mount it.

And google is your friend.