All you need to do when enabling the Walmart Marketplace integration is to supply your Consumer ID, Client ID and Client Secret. Finally, all you need to ensure is that the tick has been marked for the "Enabled" option.
A key element of this integration can be found with the setting of the Category Mapping. This means you need to add your category details from Walmart and these much accurately match whats found on the front end of Walmart.

For more details on how to set the mapping please refer to Walmart's very own documentation - CLICK HERE Additional settings that can be set on this integration include a Category Strategy, Feed Strategy, Category Mapping and an email to send any errors to.
Category Strategy allows you to pick from the following two options - Standard (Clothing) & Disney

Feed Strategy allows you to pick from the following two options - Standard & Disney
Finally you can enable an option to turn the integration into a sandbox environment by ticking the Is Sandbox Enabled and you can enable to push the inventory by ticking on the Push Inventory Enabled option.