First of all, you should download the installation package. https://my.vmware.com/web/vmware/details?downloadGroup=VCL-VCD550&productId=356&rPId=4244#product_downloads
Secondly, you should upload it to your current active vCloud Director server via any Software that I use Winscp.
I will explain what I did. Open my WinSCP and choose SCP and typed my IP address of vCloud Director. After that, wrote my user name which is “Root” and then my password. After I logged on succesfully to the VCD I copied the new version of VCD into Tmp folder. When the copy job is finished, you can close the application because you don’t need it anymore.
It is time to connect to directly to VCD server via Putty. After I logged on to the server, I typed ./opt/vmware/vcloud-director/bin]# ./vmware-vcd-cell maintenance
The cell will response to all request to maintenance mode. If you have a load balancer, basically, you can block the acces to the cell you want to upgrade.