You need to know the name of the activity, the code below will open the Help Activity directly:
Dim in As Intent
Dim pm As PackageManager
in = pm.GetApplicationIntent("com.xtralogic.android.rdpclient.trial")
If in.IsInitialized Then
in.SetComponent("com.xtralogic.android.rdpclient.trial/.HelpActivity")
StartActivity(in)
End If
However, this app it doesn't allow its activities to be called in this manner, they have to be called from the Main Activity, the only one that can be called in this case is the HELP, but at least now you know how to call activities directly.