First and foremost, these promos are ONLY available to NEW users of Youtube, and Spotify. If you have ever had a subscription to either then you are in-eligible for these promotions.
As @SHADOWGATE mentioned, you claim these promotions in their respective app, it is technicaly not a samsung promotion, but one from the respective companies.
@useroB1TgHoSoB The promotion does not come from Samsung, and has been available to you since you powered on your device, go into the respective app and search for it within their menus for a promo. If it is not there then perhaps you are in-eligible as you have subscribed to either service already.
Finally I do not believe this is a Youtube TV promotion, but istead a Youtube Premium (no ads) one. I could be wrong here but that it what was running when I purchased my device.