Recently I wanted to add an Arduino library to EESchema to make a schematic. Here’s how to do it.
Download the Library Files
First download the library from somewhere. I found the library I wanted on GitHub, but there are other places you can look, too.
Add the Library Files
Whether you downloaded a singled zip or multiple files, make sure you’ve located the .lib file. That’s what you’ll be adding. Open EESchema and open the Preferences > Library Menu. It should look like the window below.
To the right of the Component library files pane, click Add. Locate your library file and add it. Click OK.
Now when you go to place a component, List All to see all your libraries and you should see your new library in the listing. Click on the library to choose your component and put it on your sheet.