Open the Ziina app and tap My Violet on the home screen. Select Deliveroo and tap and hold Reveal Code to get your unique promo code. Open the Deliveroo app, go to Account → Vouchers & Credit, and paste your code. Tap Try free for 12 months to activate your Plus Silver subscription.
Note: if you already have a Deliveroo Plus plan, cancel it first — then redeem your code once it ends. Your code is single-use, so keep it safe.