Under Construction

Just starting out with WordPress and developing my own Web site for the first time. I want an “under construction” page on my web site because the dummy page is embarrassing and I need time to figure this out behind the scenes.

I downloaded both “under construction” plug-ins. First, I downloaded one by Jeremy Massel. I activated it, worked with the settings. But my dummy page was still up there, so I de-activated it and downloaded a second, by Mario Kostelac. Worked with the settings, and have it activated, but still, the dummy page is up there.

What am I missing here? I searched the plug-in basics, albeit quickly, and it had said the plug-ins have instruction files to follow. I did not see an instruction file.

My question: What’s the simplest, most user-friendly way I can get a simple “under development” message up on my site, instead of a dummy site?

And, it feels like I’m missing a basic instruction of making a plug-in work …

Thanks in advance for the help!