Im trying to set up a wired connection throughout my house so i can use eth

Im trying to set up a wired connection throughout my house so i can use ethernet in every room, and i don’t really know what to make of this. To be clear, there are already set up ports as seen in the picture, I just don’t know how to connect them to the router/splitter. I moved in to this house so I am not the one who put this in. Any feedback would be greatly appreciated.

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