You should always seek advice from an electrician prior to installing your shower and also view the installation instructions in this regard
3kw Steam Showers (without Whirlpool baths) require only a single 13amp electrical supply. Shower with whirlpool require two connections
Typically the shower is supplied with a standard UK 3 pin plug – this is used for testing ONLY and this is removed when you install as the use of sockets within bathrooms is dangerous/illegal. Please refer to a qualified electrician who will be able to install the shower via an Isolated Fused Spur.