So ...

Upon activation, go to Settings => WP Maintenance Mode to access the plugin configuration page. It's a multi-tabbed page with five tabs. Let's see the first "General" tab:

First of all, you'll have to select the "Activated" radio button under "Status" in order to actually activate the plugin.

If you want search engines to be able to see your website while it is in construction/maintenance mode, then you'll have to set the "Bypass for Search Bots" option to "Yes" (recommended).

Obviously, as an administrator, you'll have full access to your site's backend and frontend area during the maintenance mode. The plugin will allow you to specify which other user roles should be allowed to access the front and backend of the website while it is in maintenance mode.

The other options are self-explanatory ... Once you are happy with your choices, don't forget to click the "Save settings" button.

Then, you can move to the second "Design" tab. This is where you can create customized landing pages to display during maintenance mode:

You can start by providing a title, a heading, and some content to display on your maintenance page. Of course, if you want to create a coming soon page, you can change the content accordingly ...

Then, you can define the text color and background type. Once you are done, click the "Save settings" button.

OK. Let's see the third "Modules" tab ...

If you are planning to put your site in coming soon mode or just want to let users know when your site will be up again, then you can use a countdown timer module. Simply select a start date and enter the remaining time:

Also, you can also allow users to subscribe and be notified when your website is back online (they will be notified via the plugin, and they will NOT be subscribed to your email list!):

More than that, you can add links to your social media profiles in the coming soon mode or maintenance mode page! Simply enter your social media profile URLs, and the plugin will automatically display the social buttons:

The next "Manage Bot" tab will allow you to set up a pre-programed live chat bot which includes an interactive conversational help box:

What you need to know: if you enable the bot, then it will hide the maintenance mode content you had set on the "General" settings tab!

Finally, the last "GDPR" tab will allow you to enable the privacy module and select your privacy policy page:

And that's it! Now let's see the result ...