If you need to access to JCS (Java Cloud Service) from DevCS (Developer Cloud Service), for example you need to do this when you deploy something from DevCS to JCS, you must enable an SSH communication with pub & private keys between DevCS and JCS.
You must obtain a key from DevCS and insert this key on JCS.
To obtain the key from DevCS you can do a REST call:
The red part is tipical of your DevCS environment, is the url that you have after the login on your DevCS.
You must use the same user and password that you use in the login of DevCS, in the next image you can see a sample of rquest with Postman on my domain :
Now you need to copy the highlighted part as you can see in the next image:
Access to JCS with Putty:
[How to access in SSH to Oracle Cloud using Putty and ppk key]
Paste the highlighted part in the authorized_keys.
In the next image you can see the new inserted part in my authorized_keys ...
That's all !!!