How can I release the captured payment in PayPal sandbox?

How can I release the captured payment in PayPal sandbox?

I have block (Authorization) some amount from customer account by using
the following form.
<form:input path="cmd" id="cmd" name="cmd" type="hidden" />
<form:input path="business" id="business" name="business" type="hidden" />
<form:input path="password" id="password" name="password" type="hidden" />
<form:input path="custom" id="custom" name="custom" type="hidden" />
<form:input path="item_name" id="item_name" name="item_name" type="hidden" />
<form:input path="amount" id="amount" name="amount" type="hidden" />
<form:input path="currency_code" id="currency_code" type="hidden"/>
<form:input path="rm" id="rm" name="rm" type="hidden" />
<input type="hidden" name="return" value="${paymentForm.returnUrl}" />
<form:input type="hidden" name="paymentaction" path="paymentaction"/>
<form:input type="hidden" name="cancel_return" path="cancel_return" />
<form:input type="hidden" name="cert_id" path="certId" />
</form:form>
Now I want release the blocked amount. How can I do that?
Thanks In Advance
Lakshmi Priya.K