Trying to work on my site with plain one live OR using a maintence plugin

I have read so many threads on this now, but I am such a noob I don’t understand them. Then, I try to look up the stuff I don’t understand and it gives me more stuff I don’t understand. I want to cry!

My site sucks, I’m trying to jazz up the theme, add pictures, once I do that add some plugins, etc. The problem is, it’s going to take a while so I want to either do it somewhere else or have a maintenance mode page. If you can believe it, I can’t accomplish either of these things.

I was first trying to figure out how to work on my site with my current one live. I read a lot about subdomains, folders, databases, and stuff like that and I don’t know what ANY OF IT IS or how to make or get to any of it. I thought maybe I just need to play around on my dashboard and I’ll find the stuff, but so far that has not proved fruitful. Is there an easy step by step for someone who knows NOTHING about web stuff, or have I just gotten in over my head using www.remarpro.com?

Next, I decided to use maintenance mode plugin, but after I unzip the plugin folder I have no clue what to do. Pathetic? Yes, but I’m willing to learn I just need to start at step -1 or something like that.