Go to your Amazon seller central and login with detail to click here https://sellercentral.amazon.com/

After login Visit this link https://sellercentral.amazon.com/marketplacedeveloper/applications.

You can see here Developer Central Information

Click on View Button for see MWS credentials with all keys in Popup.

Go to your Ebay account and login with detail to click here https://go.developer.ebay.com

After login Click on first menu then.

Open dropdown menu and click on this "Application access keys".

Click to create new key set link.

Your keys consist of three IDs:

Table: Development Keys

Value	Meaning
DevID	Unique identifier for the developer's (or company's) account.
AppID	Unique identifier for the application.
CertID	Certificate that authenticates the application when making API calls. Not to be confused with user-level authentication tokens.
Authentication tokens	Getting Tokens for information about generating and retrieving authentication tokens for each user.Once you have your development keys, see

Step 1: Go to admin

Step 2: Add REST Roles ?

Step 3: Set REST Attributes

Step 4: Add OAuth Consumers

Step 1: Go to admin

Step 2: Click on system tab then click on integrations tab.

Step 3:Click on Add new Integration and fill the all integration info.

Step 4:Click on API and set the access.

Step 5:Now click on save button.

Step 6:Now click on Activate and open a popup press Allow button.

Step 7: You can see here all details of configuration.

Step 8: Copy the all required credentials here

How to generate API key for my Shopify Store?

Step 1: From your Shopify admin, go to Apps.

Step 2: Click Manage private apps, near the bottom of the page.

Step 3: Click Create new private app.

Step 4: In the Description section, enter a name for the private app and a contact email address.

Step 5: Shopify uses the email address to contact the developer if there is an issue with the private app, such as when an API change might break it.

Step 6: In the Admin API section, select the areas of your store that you want the app to be able to access.

Step 7: If you want to use the Storefront API, then select Allow this app to access your storefront data using the Storefront API. This will generate a Storefront access token.

Step 8: Click Save.

You'll see your API key and password in the Admin API section. You can use these credentials to make authenticated requests to the Shopify store that uses your application.