After uploading the product, If there is no error, it will not show instantly but takes few minutes to process Item feed request and once it processed on Walmart your product will be visible on Walmart.
You can also check Feed status in your Magento 2 store under Walmart > Walmart Products >  Product Feeds.

You cannot add discounts but you can add special price for any Item.
If any Item has special price, special price will be sent to Walmart.

Product tax codes can be set globally for a Walmart category or individually for each product.

When an order is generated on Walmart.com, then the merchant should notify Walmart.com that whether he is able to fulfill the orders or not.

For this purpose:

Go to Walmart > Walmart orders >  View Walmart orders, Orders will auto fetched and acknowledged while cron runs at every 10 min.
If you need to cancel the order, you need to enter quantity cancel equal to the quantity ordered in shipping by Walmart tab comes under order view.

Please refer to our blog link of How to get API keys from Walmart Marketplace provided below:
https://cedcommerce.com/blog/walmart-marketplace-api-integration/.

To install the Walmart extension :-

• Login to your ftp and go to Magento 2 root folder (generally present under public_html folder) 
• Create new folder named code under app folder and under “code” folder create a folder named Ced.
• Drag & Drop app/code/Ced/Walmart directory.
• After successfully uploading the directory, the extension will be installed/upgraded. 
• Now run the following upgrade command in “cmd” php bin/magento setup:upgrade
  

Due to any reason if an error occurs during the product mass upload then customer can get Item feeds
from Walmart > Walmart Products > Product Feeds

To see the feed errors click upon the ERRORS Link on the corresponding feed .

There are following reasons that an order may not fetch from Walmart to Magento 2:

1.Stock Qty < = 0
2.The product is disabled.
3.The product is out of stock.
4.Walmart Ordered item qty > Magento Order Item qty.
5.Product SKU is not present in Magento.

Customer can get failed orders and reason from Walmart > Walmart Orders > Failed Imported Orders

You can use the Validate Button for this purpose under Walmart > Configuration > Walmart API Settings . Please enter the details and click on Validate.

The Inventory of product is sent after each product is submitted to Walmart but since Walmart takes some time to process the feeds, the inventory feed can fail for some particular SKU. In that case, you can select the products from our grid and choose the "Update Inventory" option to sync product inventory between Walmart and your Magento 2 Store.

If you are validating a configurable product for Walmart Products Check, then its variant attributes need to be mapped under Walmart > Configurations > Configurable Attribute Mapping. Once after saving the mapping here please re-validate the product to see the result.

The User Guide for our extension is available at the below-given link:  https://docs.cedcommerce.com/magento-2/walmart-magento-2-integration-guide-0-0-1/