Connecting a shower is complicated procedure and should generally not be tried out by novice DIY home enthusiasts.
Additionally, as describe elsewhere, there are several regulations that you will need to comply with.
Consider things such as
- An independent permanently connected supply must be obtained from an individual unit to your shower
- A switch is needed.
- The switch must be readily accessible and clearly identifiable.
- The switch must be out of reach of a person using a fixed bath or shower.
- A cord operated switch is ok.
If you do set up the shower on your own, you might need to have the appropriate inspections to ensure that your installation is in accordance with regulations.