You are about to read a tutorial written by a member of this website. Although the author probably invested every effort to make this tutorial's content correct, we can not guarantee that the information on this page is 100% exact. Please keep this in mind when reading this tutorial. ;o)
The first thing you might be wondering about is where to get the plugins from. All you have to do is , visit the paint.net official forums
here.
Here is my favorite
once you have chosen your plugin, there is a download link or button.
If there are multiple mirrors, it doesn't really matter witch one you use to download. You can choose whichever you want. And, if you have a preference, go ahead and use it. It also doesn't matter whether you download it as a .zip or .dll. Just remember that if you download it as .zip, you will need to extract it.
Try to remember were you save the file, you will need this information during its installation.
This should be all you need to know about downloading the plugins onto your computer. Now, you've got the file. read on to know how to use it

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Now that you have the file on your computer, we need to put it in the appropriate folder so that Paint.NET can detect it & use it.
This is why you needed to remember where you downloaded the files to. First of all, open Paint.NET's installation folder (usually, it's located in C:\Program Files\Paint.NET, but it depends on the way you installed it.
Please Note:
paint.net is not supported, nor is it planned to be supported on other platforms than Windows. So unfortunately, you can't use Paint.NET using a Macintosh. However, you may be able to find a program [Emulator] to run it on Linux.
After, you have to open the effects folder, move the plugin you downloaded (in the first chapter) in this directory.
Restart Paint.NET if it was opened. You should now be able to use it

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Most plugins show up in effects>render in the upper toolbar.