Create server:
hcloud server create --name=myserver --image=ubuntu-18.04 --type=cx31 --datacenter=hel1-dc2 --ssh-key=vitich

List our servers to get server ID:
hcloud server list

Add floating-ip
hcloud floating-ip create --type=ipv4 --home-location=hel1

List floating-ip to get floating-ip ID:
hcloud floating-ip list

Assign floating-ip to server
hcloud floating-ip assign 12345 myserver

More info about hcloud on github
or Google :)