Yes, providing credits is mandatory when using our music in most cases*. Both the composer, Peder B. Helland, and Soothing Relaxation should be mentioned in the credits.
The credits can for instance be written like this: "Music (<INSERT TITLE>) by Peder B. Helland, licensed by https://soothingrelaxation.com."
* There are special rules if you purchase the Guided Meditation license. Click here for more details.