PayPal DoCapture “you don’t have permission to make this API call” Error

PayPal DoCapture "you don't have permission to make this API call" Error

I have tested doCapture API call by using the following form
<form method=post action=https://api-3t.sandbox.paypal.com/nvp>
<input id="METHOD" name="METHOD" type="hidden" value="DoCapture" />
<input id="AUTHORIZATIONID" name="AUTHORIZATIONID" type="hidden"
value="4M894622FJ6713130" />
<input id="AMT" name="AMT" type="hidden" value="50" />
<input id="CURRENCYCODE" name="CURRENCYCODE" type="hidden" value="EUR" />
<input id="COMPLETETYPE" name="COMPLETETYPE" type="hidden"
value="NotComplete" />
<input type=submit value=DoCapture>
But it show the following result
TIMESTAMP=2013%2d08%2d08T04%3a42%3a31Z&CORRELATIONID=d5019d565a403&ACK=Failure&VERSION=0%2e000000&BUILD=7161310&L_ERRORCODE0=10002&L_SHORTMESSAGE0=Authentication%2fAuthorization%20Failed&L_LONGMESSAGE0=You%20do%20not%20have%20permissions%20to%20make%20this%20API%20call&L_SEVERITYCODE0=Error
How can I set permission to make this API Call?
Thanks in Advance
Lakshmi Priya.K