Hi,
I want to install a Shelly Pro 3EM to measure my jacuzzi. Before connecting it, i want to be sure i am doing it right. Could someone (with the appropriate knowledge 
) confirm or correct the following:
The clams will be connected in the red area (cables are there but no very visible); the power connection would then be done in the yellow zone (upper left).
That would be your local qualified electrician if you are unable to follow the user guide supplied with the 3em.
Mains power connected wrong to a item that has lots of water you are immersing yourself in is going to be in the evening news. Get proper help.
Adding to that…
DANGER
No one here can see or check what your home wiring is. The best you will get is guesses, and you have no idea if the person ‘helping’ has any idea or not.
Keep in mind if you know what you are doing, I have no problem helping. But when you clearly do not know anything about the wiring you are looking at then PLEASE get help from someone that does.
Disclaimer
DANGER OF ELECTROCUTION
If your device connects to mains electricity (AC power) there is danger of electrocution if not installed properly. If you don’t know how to install it, please call an electrician.
Beware: certain countries prohibit installation without a licensed electrician present
Remember: SAFETY FIRST. It is not worth the risk to yourself, your family and your home if you don’t know exactly what you are doing. Never tinker or try to flash a device using the serial programming interface while it is connected to MAINS ELECTRICITY (AC power).