Arnie,
This is what I would do to get this up and running.
You will need to down load a sd card formatter and an image writer app. I would also purchase a new sd card so you can start fresh and have the original sd card for backup.
https://www.sdcard.org/downloads/formatter/ for sd card formatter.
https://sourceforge.net/projects/win32diskimager/ for image writer
My opinion this is the easiest way to get going. You will not have to deal with hidden passwords and you can learn the process of getting the program installed on a new sd card.
here is a sd card link from Walmart
https://www.walmart.com/ip/16GB-microSDHC-Class-4-Flash/100296336
Here is a sd card reader example from Walmart again
https://www.walmart.com/ip/onn-SD-Micro-SD-and-CompactFlash-Card-Reader/940592168
Now with all this stuff in hand your now ready to get the sd card prepared and the software loaded on it.
Here is the link from Brian`s GitHub site that will walk you through this whole process and give you a lot more info about the project.
https://github.com/CapnBry/HeaterMeter/wiki
Go down to the "Installation" section and follow instructions.
This should help you get your HM going and help you learn what this great project is all about. All your previous questions I hope can be answered in Brians GitHub link. When I first got started, I too experienced trouble getting this project up and running on the wireless connection side. I re-read the GitHub info and from there I posted a question which was answered and at that point I felt I was on the correct path. By following this path with a new sd card, you can make mistakes and with a little trial and error, you should get this up and running. If the HM doesn`t work, you just remove the sd card, reformat and install the image back on the card and start over. You will always have to connect to your router with an ethernet cable following this path the first time in order to set up your WIFI. I do believe it always comes up as 192.168.200.1
Once there you can get into the configuration page and go to the WIFI section in the GitHub instruction and then setup up your new password and then your WIFI connection. One other thought on the WIFI side, if you're not in a hi WIFI traffic area I would stick to the 2.4ghz band because you have better signal strength which will give you better connection. I have used both the 5ghz and the 2.4ghz bands and I just have better results with the 2.4ghz band.
Hope this helps.