Cube + set up manual or pdf, etc

I just received my Cube+ and here3 compass. I am brand new to this and not to computer intelligent.
Is there an install manual or pdf, etc. with step by step instructions on how to do the needed downloads.
I tried to follow instructions on a couple videos, but have had no luck.
So far I have only been able to install Mission planner on my PC, hook my flight controller to my PC via the mini usb cable and try to connect. It wants me to choose port but the ones it offers me to choose from, none work, I can not connect. I did not get any instructions with the Cube+ Is there a website I can go to with step by step instructions?
any help would be greatly appreciated.

Thank you

Hi Steven , there is no firmware installeld in new cube, you can program firmware with MP.
Please check the following link for more guides

I faced issues with Ardupilot script.
Usually it works, but sometimes it times-out on erasing flash.

What is the version of bootloader shipped with the cubeOrganePlus
how to know that?