To authorize a Walmart instance, go to the Plugin Settings page (Settings > Plugins). Select Walmart, and then create a new Walmart instance.

Before you can enter your Client ID and Client Secret, you will need to go to your Walmart Seller Central account and get those values. 

Sign into Walmart Seller Central and navigate to Settings > Consumer IDs & Private Keys, then click on Visit Developer Portal. You'll be taken to the developer portal and automatically signed in.

Or, go directly to use you Seller Central credentials to sign in as a US Marketplace Seller.

One you're signed into the Developer Portal, click your name at the top of the page and click on API Keys.

You should see the following screen:

You should be able to copy your Client ID and Client Secret and will be able to enter them in the Walmart plugin screen within SureDone.

After you get the Client ID and Client Secret values, you can put them in their appropriate fields in your Walmart Plugin Settings

Then you can click Authorize to successfully link your Walmart instance to SureDone.