Without knowing what exactly you are going to do, it's quite hard to provide you with the steps. For an ESXi host, you'd basically start with checking the VMware Compatibility Guide to ensure that your hardware is supported, then configure the host's BIOS and finally install ESXi. Once installed configure the network and time server settings, and enter the license key. There might be other features which you need to configure depending on your needs, e.g. storage connection, vCenter Server, ... I'd suggest you take a look at the VMware vSphere Documentation for further details.
Also note End of General Support for vSphere 5.0 and vSphere 5.1 (2145103) is August 24, 2016. If you hardware supports ESXi 5.5 or 6.0 you should consider to use one of these versions.
André
