vSphere Management SDK url is just blank page

I'm trying to get started using the vSphere API, reading the document at the link below I should be able to browse to my vcenter using "sdk" in the URL but it's blank. Also I read that you have to download the root certificates, but that link is not where this document claims it is. I'm using 5.5

https://vdc-download.vmware.com/vmwb-repository/dcr-public/2d445149-7707-4c7d-98a7-9f00394b7df2/7322d611-ef3b-454a-ab63-ad3302d8b218/SDK/vsphere-ws/docs/SDK-README.html

Do I need to enable this SDK in vCenter?