Graphics card problem?

The R9 360 has a TDP of 100 watts. a PCI-E slot can supply 75 watts of power at most. So therefore that extra 25 watts needs to come from somewhere. Your card does require a 6 pin PC-E power adapter.

" Where do I connect the power supply to if I bought a cable?"

I'm guessing you have a cheap/generic PSU. a quality 500 watt PSU will have two 6/8 pin PCI-E power adapters while questionably-made ones don't. You can try and get a molex to PCI-E connector if you have some extra 4 pin molex power connectors left on your PSU, your video card probably came with one actually. But other than that, replace the PSU with a decent one.

Put it this way, if your PSU does not have the necessary 6 pin PCIe video power connector, then that PSU is NOT designed to run a video card that needs one. Upgrade the PSU and your problem will be solved once you wire up the proper power.

Your PSU should have PCI-E connectors (6-pin); it would be odd if it didn't. One can also use a Molex 4-pin to 6-pin PCI-E gender changer.

you get a gender changer for one of your spare hard drive(MOLEX) connectors. so you need a molex -> pci-e cable