How to use of pay pal java API

I am developing web application in that i have included pay pal payment system, i am making use of java API my, i have got API key, password and API certificates also, but i dont no where to use that, i have gone through the documentation w开发者_如何学Gohich is in pay pal but didn't get solutions please help me out. i have downloaded samples from the below links: https://cms.paypal.com/us/cgi-bin/?cmd=_render-content&content_ID=developer/library_download_sdks

Here you can get some guidance:

• Copy 'adaptivepayments-java-sdk.jar' to your class path.
• Copy the configuration file 'sdk_config.properties' in SDK 'resource' folder to your project.
• Import AdaptivePaymentsService into your code.

• Load the configuration file into your application with this method call as required:

  new AdaptivePaymentsService(new File(".../sdk_config.properties")); 
  

• Create a service wrapper object.
• Create a request object as per your project needs.
• Invoke the appropriate method on the service wrapper object.