Upgrade PowerEdge 2970 ESXi 4.0 to ESXi 5.5

I have a 2970 with ESXi 4.0 preinstalled by Dell.

I want to upgrade it to ESXi 5.5

Is there any documentation for this?

I have downloaded the VMware-VMvisor-Installer-5.5.0-1331820.x86_64-Dell_Customized_A00.iso.

Regards

Lewis