Refere this article to create a custom button on the Quote Detail page to launch a Hosted Payment Page.

1. Create a custom Visualforce page, named CreateCreditCard , using the standard controller zqu.Quote__c and the CustomHostedPage created in the pevious section: <apex:page standardController="zqu__Quote__c"> <apex:include pageName="CustomHostedPage"/> </apex:page>
2. Navigate to Setup > App Setup > Create > Objects , and click Quote .
3. In the Buttons, Links, and Actions section, click New Button or Link .
4. Create a new Page Button. In this example, the button is named "Create Credit Card".
5. Enter the rest of the required fields as shown below.
6. Click Save .
7. Click the link, Back to Custom Object: Quote.
8. In the Page Layouts section, click Edit next to the Quote Layout - Default V6.1 page layout.
9. Click Buttons , and drag the newly created button to the button bar.
10. Click Save .