Hi @akmsaarif

Now you can connect to your server via SSH/SFTP to upload files. You can use many different clients to transfer files, among other Cyberduck, Filezilla or WinSCP, but have a look at this tutorial:
https://www.digitalocean.com/community/tutorials/how-to-use-filezilla-to-transfer-and-manage-files-securely-on-your-vps

If you need help connecting with the server to setup a service, you would use SSH:
https://www.digitalocean.com/community/tutorials/how-to-connect-to-your-droplet-with-ssh