You can only access the powered by Instacart BJ’s site if you have a membership and a login for BJs.comAt this time, BJ’s branded credit card rewards and membership rewards are not accumulated with orders placed through the powered by Instacart BJ’s site. Membership benefits/offers are also not applied at checkout.

Disclaimer from BJ's: 

Please note that purchases made through this platform for same-day delivery by Instacart are not “Eligible Purchases” for BJ’s Perks Rewards® Members or under the My BJ’s Perks® Program. See bjs.com/terms and bjs.com/perkterms for full information on Eligible Purchases.