How to credit Nihilore:
For a Youtube video, put the name of track and "by Nihilore" in the description of the video with a link back to this website
Otherwise
Put the name of the track and "by Nihilore" in the credits, or if multiple tracks are used a simple "music by Nihilore" will suffice
If there's a place where the credits are put online, try and provide a link back to this website
For more detail see the License page