So ...

Upon activation select the new Mega Menu link in the admin area in order to access the main settings page:

The default settings usually will work for most websites.

But, you'll have to customize the menu colors, so they match the colors used by your theme. Which means that you need the hex code for those colors ...

If you know those codes, you can skip the next part. If you don't, here's the how ...

You could right click on your homepage and select "Inspect" to find the hex code of your menu colors in the source code itself. But, that could be quite annoying ...

So here's an easier solution ...

Take a screenshot of your main menu (with a highlighted active item included). Then go to ...

https://pinetools.com/image-color-picker

... upload your image and click on your menu colors to get the hex codes:

Write them down (or even better paste them into a text file), go back to the Mega Menu plugin, select Menu Themes => Menu Bar and enter (copy) the hex codes in the "Menu Background" and "Menu Item Background" fields to match your theme colors (click the small black squares and replace the rgb values with your hex values):

Finally, save your changes.

Now you are ready to create your new mega menu.

So let's move forward to see the real magic ...