I bought this unit I am not sure if this is suppose to generate a WIFI signal when pluged into AC as it has no ac plug maybe have take screws out and open unit up and wire DIRECTLY instruction don't tell you nothing.Send it back to the vendor.
It should have come with some documentation.

Do you need a Wi-Fi repeater?

What you have there is a wall outlet. You take out a regular AC power wall outlet in a room, and then wire this device to the house power in its place and put it back in the hole in the wall. You do this with the house AC power switched off. If you don't KNOW exactly how to do this safely, you need an electrician. Inside the device is a router with wi-fi and a USB 5 volt power supply. You press the button to connect to your existing wi-fi and you get stronger w-fi in the room and ethernet connection. Read the manual! It has a USB charger socket, an RJ45 socket for wired network cable (ethernet). Once it is installed, you can't use that outlet for AC power any more.