Yeah, I don't think you quite understand what ESXi is. It's a hypervisor - it takes the place of your host OS. VMWare Workstation is a virtualization program which installs on a system running Windows or Linux. VMWare ESXi is basically its own OS and virtualization program wrapped up in one.
So you install ESXi directly onto the server. Then you install VSphere Client onto a different computer, and use it to connect to the ESXi server. Then you can transfer install ISOs to the ESXi server and create and install virtual machines on it.