@boukadidahadil69 Apologies for the delay in replying. You are trying to connect to the virtual machine via putty ? or are you connecting to the DigitalOcean server?
You require Putty when connecting to DigitalOcean server. However if you are using VirtualBox or VMware then you don’t require Putty. When you start the virtual machine it will automatically SSH you into the box.
Let me know about the above queries so that I can help you further.