From the pic it is a KS-AX3102 model (now obsolete) from JVC. The wire shown disconnected (blue thin cable near to RCA) in your pic is near to 'speaker input connector' jack, used if there is no Line-out/pre-out from the HU (It can't be that, you already have RCA cables from HU). Or else it may be a ground connection (but why there on this side!). The power connections are on the other side of the amp, refer the pic below or the
JVC drvn KS-AX-31XX Operation manual, check the power connections using a multimeter or some spare lamps.
PS: While posting such queries add details like model number and your current setup, or else upload a closer pic. It will be more convenient for people to help you.
Image Source: support.jvc.com