WirelessHART requires a Network Manager, a Gateway and a minimum of  five (5) WirelessHART field devices.  

You will also need a Handheld master to configure the join key and network ID in the WirelessHART field devices.

The field instruments would need a WirelessHART Adapter if they are not WirelessHART products themselves.  WirelessHART uses IEEE802.15.4 2.4GHz radios, with a range of 200m between devices within the network.  It is recommended to use two (2) Gateways for redundancy.  

Attached is a WirelessHART Engineering Guide, see section 8.6 (Designing) for the rules of installation in order to have a healthy WirelessHART network.