Simply place the following tag in your post wherever you want the web form to appear:
[grwebform wid=”PUT_WEBFORM_ID_HERE” css=”on/off”].
Set the CSS parameter to ON, and the web form appears in GetResponse style; set it to OFF, and the web form appears in standard WordPress style.
You’ll find your web form ID right in your GetResponse account. Go to Web Forms => Web forms list and click on the “Source” link in a selected web form. Your web form ID is the number you’ll see right after the “?wid=” portion of the JavaScript code.