Why you need ssh key for cloud server ?
This is one time setup which enable quicker and safe login experience . Username ,password login is no longer safe and reproducible. Switch to ssh login for quicker and secured login system.
How to generate it ?
Step 1: ssh-keygen -t rsa -b 4096
Step 2: Read keys and print it content , so you can copy-paste it in destination ssh keys (public key)
Step 3 : Login using ssh
ssh -i /path/to/ssh username@host_ip