A:
John,
Purchased the MK530 set couple days ago, it came from the factory with a unifying receiver. -- That said, you should download the Logitech Unifying software here... http://support.logitech.com/en_us/software/unifying -- very compact & easy to use. -- The advanced feature allows to you to "pair" a new device quick 'n' easy. Once the devices have been paired to a receiver, they should work flawlessly.
I've been running a K360 keyboard (purchased from BB Aug 2017) with M310 mouse off a single Unifying receiver for bout the past 6-months with no hiccups. Jurassic Dell laptop running XP Pro.
BTW: Logitech kybd's & mice that support the Unifying technology have a orange / black star on the bottom of them -- it's on top of the receivers (see attached pix).