Similar to hooking up a turntable, using a Bluetooth receiver to stream music into your receiver or amp is SUPER simple. There are many, many options from many manufacturers that have units that convert Bluetooth into RCA. I have used the TP-Link HA100, but others will work, as well. As long as they can output via RCA.
All you have to do is hook the RCA plugs from the Bluetooth unit to the AUX port on the back of the receiver/amplifier. Select AUX as the source on the receiver/amplifier and then hook up your computer or phone to connect to the Bluetooth unit. You are good to go. No ground cable needed like you see on turntables.
Remember that you can manipulate the volume of the Bluetooth source (computer/phone) independent of the receiver/amplifier volume. Remember that before streaming any music so the volume isn't set too high, initially.