Here are the steps to add content to your Library:
Login to your community and go to the "Content" section in the left menu.
Click on the gear icon next to "Library".
Click the "Add Content" button.
Drag and drop the file you want to upload, or click the "Or browse files" button to locate the file on your device.
Once you have selected the file, it will begin uploading to your Library.
For a visual demonstration of these steps, you can watch the video provided below.