OCI or Oracle Cloud Infrastructure is a cloud provisioning by Oracle which offers: PaaS, IaaS and others services. Firstly, to get access to OCI, we need Oracle account for OCI, which you can create for free at: “cloud.oracle.com” Like any other cloud infrastructure, there are whole books you can read of the architecture and the processes, but in a nutshell, you can think of it, as something like this:

Once you have your account, your tenancy and your root compartment. It is important to set your configuration. The “config” file should be in your home location under the .ssh/ folder. Otherwise, you won't be able to connect. The configuration should have something like that.

[DEFAULT]
user=ocid1.user.__
fingerprint=2d:0d:__
tenancy=ocid1.tenancy.___
region=eu-frankfurt-1
key_file=<path to your private keyfile> # TODO

Of course, use yours user and tenancy OCIDs, as well as the private key of the public key you have added as API key.