From their Facebook page:
"This weekend ONLY
Launch oBike app —- Tap [Promotions] —- Enter the promo code [Summer] —- Tap [Apply] —- and you'll receive vouchers worth 5 free rides, each within 30 minutes.
Enjoy the simple pleasure of riding a bicycle on a summer day. Get oBike app now!"
Rides have to be used this weekend, but free is free.
Worth noting ofo bikes are free this whole month - which may/may not be a better option depending on where you are.
Pretty weak promotion. Code should last all of Summer months.
OFO bikes are free all of December