Grocer looks at email receipts from New Seasons Market in your gmail and from them creates a database of your shopping history. It has no connection to New Seasons Market itself, and relies entirely on the information contained in the receipts.
The easiest, fastest way to import your receipts is to click the import button and follow the prompts to give Grocer read-access to your email. If you are not comfortable with that, you can still import the receipts, but there will be a couple extra steps.
First you need to create a secondary gmail account - Grocer will have read access to it so keep it exclusively for New Seasons receipts. Then, in your primary gmail account, enable email forwarding and create a filter to automatically forward a copy of New Seasons receipt emails to the secondary account. This is easy to do, and I made a short video detailing the steps, located at the bottom of this page.
Note that you will still need to manually forward your old receipts if you want to see them in Grocer. This is a little tedious, but if you are smart about it and get into a groove, you can get through them at a fast rate. And remember, you can also import them directly from your primary account with just a couple mouse clicks.
In parsing receipts, Grocer relies on the html structure and the information inside of New Seasons Market email receipts in order to intelligently decide what is a product, unit price, weight, etc. Their email receipts are largely consistent in their organization, but pricing information is not always perfect - for many items (mostly from behind the counters), they do not consistently provide unit/per pound pricing or thorough item descriptions. Grocer fixes some of this behind the scenes, but there will still occasionally be head scratchers like a $7 bagel (which was most likely a loaded bagel sandwich). There may also be edge cases in their email presentation that Grocer has not yet seen and does not yet know how to process. In short, it will always be a work in progress. To report any discrepencies, email firstname.lastname@example.org.