Fist off, download the Dell customized image of VMware ESXi 5.1 found here. Next, start the virtual console to the blade.
Click on the Virtual Media menu option in top left corner, then select Launch Virtual Media. Make sure that the Mapped checkbox is checked.
Click on Add Image button and browse to the ESXi 5.1 .iso image you’ve previously downloaded. Select Virtual CD/DVD/ISO from the Next Boot menu, then restart the server by clicking on Macros then CTRL-ALT-DEL.
Press F11 to get into the BIOS Boot Manager
Select to boot from the Virtual CD. At the Boot Menu prompt select Dell ESXi 5.1 Installer. Then follow the wizard to complete the installation.
Once rebooted, press F2 to configure Networking.
Under IP Configuration you can configure the IP address, subnet mask and default gateway. Depending on your environment you might want to configure VLAN ID, etc.