To connect M2E Multichannel Connect to Walmart USA, you need to get Walmart API credentials and set permissions:

1. Log in to your Walmart Developer Portal.

2. Click + Add New Key For A Solution Provider.

3. Select M2E in the dropdown and click Next.

4. Specify the permissions you want to grant Sales Channels access to.

5. Click Submit.

Once done, copy and paste the generated Client ID and Client Secret in Sales Channels > Settings > Walmart.