By existing, I want to say a non empty EBS, a formatted device 🙂

It’s very simple:

1. Use lsblk  command to view all attached devices:

[ec2-user ~]$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
xvdf 202:80 0 22G 0 disk
xvda1 202:1 0 8G 0 disk /

2. create dir and mount device:

[ec2-user ~]$ sudo mkdir /mnt/my-data
[ec2-user ~]$ sudo mount /dev/xvdf /mnt/my-data