Paypal Adaptive Plugin for HikaMarket

I want to set this up, but no instructions.
My client has given me their Paypal details, but they do not have a User Name or Signature
Are there any instructions for this?

Where should I go to create the "application"?

Could you give me a link and possibly a procedure?

This was received from PayPal support
Check your account status. Login to PayPal. Go to your PayPal Profile and click My settings. Confirm that your Account type is either Premier or Business, or upgrade your account.
Check your API settings. Click My selling tools. Expand Selling online if needed and check API access. Click Update and Add or edit API permission or View API signature.
Download the Adaptive Payments SDK and integrate the API operations into your website or application.
Test your integration using the PayPal Sandbox, as described in Testing Classic API Calls.
To get your application live, follow the submission steps outlined in Going Live with Your Application. When you submit your application to PayPal for review, the application is quickly scanned for the requests to PayPal operations. If no "advanced" operations are found, PayPal issues an App ID for the production servers at the time you submit the application. If your application uses "advanced" PayPal operations, or if your application implements a complex business model, you can expect the review to take approximately 10 – 15 days.