If you download an icon for free, you'll need to give credit to the creator. You can find attribution requirements below:
The format should be “Icon name” by Creator Name, from Noun Project. We ask that you hyperlink to the icon and Noun Project. If you can’t hyperlink in the medium you’re using the icon, then type out thenounproject.com as the source. This attribution must be listed next to the icon, below the icon, or somewhere on the project, you create to properly reference the icon.
To make it easier, free downloads include a line of text with the creator credit. You can also find medium-specific credit requirements here.
Example 1: “Tree” icon by Edward Boatman from Noun Project.
Example 2: “Tree” icon by Edward Boatman, from thenounproject.com.