Thanks again Srikat, Suresh, and Konstantinos!
I got it to work after much headache.
I tried the Full Page Background Slider here:
Unfortunately that didn't work.
The reason is the template I'm using from Theme Forest.
It auto-generates a "galleries" page.
So there is no actual "galleries" page in the PAGES area of admin.
This meant I couldn't turn off the slider on that page.
Because the turn-off option for plugin is located at page edit level.
So then I tried this and it worked.
First, through the Media page in admin, I uploaded image for background.
Image height is 1200px and width is 2000px.
Since my template had no 'home.php', I created a blank file.
Then I uploaded home.php to my themes/mytheme/... directory.
This initially messed up my pages and template.
I could not figure out why.
Turns out, I had to go into: Settings > Reading...
For "Front Page" I had to set drop down to: -SELECT-
So now I don't have a defined home page.
This made things work.
So now I had a blank screen at: http://mydomain.com
Next, I loaded a regular page on the website: /about/
Then I viewed the source for the page.
I copied everything from !DOCTYPE down to </head> tag.
Then I created <body> and </body> tags and finished with </html>
I stripped out some coding between the <head></head> tags.
Removed all in-page CSS styles applied from template.
Then I added the following code within the <body> tags:
Then I added the following code in the <head> tags.
Probably not the best way to do it but...
It's working for now and I have a headache from trying.
It's also not the slideshow I hoped for.
But it looks good with the single image filling the screen.
I could not have done this without your help.
This post helped: