A data map associates a cluster with a template. Once a map is created, you can set map values for each component in the cluster.
Select a cluster. You cannot use components directly: you must make a cluster first.
Choose Get Property User Data Map New Templated Data Map. A picking session starts.
Pick the desired template. (A template is really just a custom parameter set, so you can actually pick any custom parameter set.)
A user data map is created for the cluster.