Go to http://applications.mercadolivre.com.br/list
Step 1: Click the Create new application button
Step 2: Fill in the fields as shown below:
* Name: Name of your store or app
* Short name: Short name of your store or app with no space
* Description: Description of your store or app
* Redirect URI: http://www.yourdomain.com
Scopes: * Select read, write, and offline_access
Topics: Select items, orders, questions and payments
Select I have read and I agree with the Terms of use. *
Click the Create application button
Step 3: After getting the App ID and Secret Key.
Access Control Panel
After login click Settings >> Free Market. Edit the App ID and Secret Key fields