To add a 3rd node:
Deploy and initialize the OVF for the 3nd vApp node.
Connect to the vApp web ui of node 1 or 2 (it doesn’t matter which).
Get to the deployment Setup screen (the screen where you drag and drop services to nodes).
You should see your 2 node cluster with all the services you already deployed.
Add the 3rd node to the node list (this scales the vApp cluster to 3 nodes).
Drag services you want to the 3rd node and deploy the solution.