To create an app,

1. Copy the Redirect Uri from Mlibre Configuration Settings and paste it in MercadoLibre Seller Panel.
2. Now choose the country from the Mlibre Seller Panel.
   
3. Login to your account.
   
4. Goto Test and click on Create New Application.
   
   
5. Paste the Uri generated above in the respective fields as shown in the image below.
   
6. After clicking on Create, the App ID and Secret Key will be generated.
   These IDs generated will be used while creating a new account.