Would someone be kind enough to explain how i can obtain the pink mercy sprays/icon
Simply log onto twitch.tv and link your Battle.net account. Then find any of the eligible streamers during the promotional period and watch up to 6 hours of their content to earn the rewards. Full details in my Twitch Rewards guide here (yes updated with information for the Charity Streams):
Have a Twitch account. Connect your Twitch account with your Battlenet account. Watch the streams listed for the charity.