“Tasks” → “Goals” → “New goal”: what it is (ice cream, the cinema, a toy — anything), a picture — a ready one or your own photo — and the price in Piri coins. The hint below says about how many days it will take. The child sees the goals in their “Jar” → “Goals”, picks “Make it the main one” and sees how far there is to go; on your side the main goal is marked “★ Main”.
When there are enough coins, the child taps “Get it” — the coins are set aside and you get “… wants to get “…” for N Piri coins”. “Confirm” — the goal goes to “Waiting to be handed over”; hand it over as agreed and tap “Handed over”. “Not now” — the coins go back to the child (they also come back by themselves after 30 days without an answer).
The child can suggest a goal themselves — “Suggest my own goal”. You'll get “… suggests a goal: “…””: set a price and tap “Add to goals” — or “Not now”.