This offer can be found underneath the 'boosts' in the ER app. You then need to link your ER account in the Milkrun app.
I believe 3500 Everyday Rewards points gets you $26.25 of Woolworths groceries, in the long run. A new $15 voucher is loaded to use in the ER app every time you've racked up 2000 points.
Other things to consider:
Coupon KIAORA10: $10 off a $40+ spend, if completely new to the Milkrun app
Dosh debit card: 7% doshback on Milkrun orders, when clicked through from the Dosh app's deals page.
ShopBack: 2.5% cashback on Milkrun orders
CashRewards, KiwiWallet and others: I'm unsure of their cashback rate
I'm keen to confirm where it says "on your first purchase", they just mean that everyone gets this deal once only. If you think it actually means you need to be completely new to using Milkrun at all, just let me know.
Be aware the item prices won't look like a very good deal to you in Milkrun, but as an example, if you wanted to stock up on say x10 Dilmah Loose Leaf Tea Premium Ceylon 250g, at Woolworths in-store it'll cost you $65. Using Milkrun, the initial price is about $68 today, but then you'll get the $26.25 worth of ER points, maybe $4.76 of Doshback at the start of next month.
I’ll give this a go just to get the vouchers to use towards petrol.