adanac,
Congratulations on your prchase, I am sure you will love the 450, it is a great flyer and pretty easy to fly.
First of all you need to bind your TX/RX, if they are not bound. This is not part of the DJI system but part of your radio system. If the kit did not come with manuals, you can download them for the TX/RX.
Do the binding with the props off.
Once they are bound. Still with no props on the 450. Hook the USB cable up to the Naza/WKM, on a PC or Mac with PC emulation and the latest Assistant SW installed, then install the driver. This is all in the manuals that can be downloded from the DJI web site. And there are lots of videos showing how.
When you have Assistant running with the 450 hooked up you can configure and check everything. Then label all the switches and make sure FS setup is correct.
This is a bit complex but you really need to learn this in order to be able to maintain your MR.
I would start by looking at all the videos and reading all the manuals, it will become clearer as you learn.
Then you can ask specific questions here if you still have problems and we will help as much as we can.