Magento Add Instructions to Purchase Order Method on Onepage Checkout - magento

Question

Magento 1.9.1 allows for payment instructions for Bank Transfer and Cash on Delivery, however, there isn't an instructions option for Purchase Order. I'd like to have the same box type below the Purchase Order Number field when the user selects Purchase Order on the checkout. How can I add Instructions in the following places:
Admin Configuration (Purchase Order)
One Page Checkout Payment Type: Purchase Order
Order Review - Payment Method
Receipt / Invoice Page
Purchase Order (No Instructions)
Bank Transfer (Instructions)
Bank Transfer (Payment Method Instructions)
Admin Configuration

Answer 1

I ultimately solved this by going to app/design/frontend/base/default/template/payment/form/purchaseorder.phtml and edidted the source code here.
From this:
<ul class="form-list" id="payment_form_<?php echo $this->getMethodCode() ?>" style="display:none;">
<li>
<label for="po_number" class="required"><em>*</em><?php echo $this->__('Purchase Order Number') ?></label>
<div class="input-box">
<input type="text" id="po_number" name="payment[po_number]" title="<?php echo $this->__('Purchase Order Number') ?>" class="input-text required-entry" value="<?php echo $this->escapeHtml($this->getInfoData('po_number')) ?>" />
</div>
</li>
</ul>
To this:
<ul class="form-list checkout-agreements" id="payment_form_<?php echo $this->getMethodCode() ?>" style="display:none;">
<li>
<label for="po_number" class="required"><em>*</em><?php echo $this->__('Purchase Order Number') ?></label>
<div class="input-box">
<input type="text" id="po_number" name="payment[po_number]" title="<?php echo $this->__('Purchase Order Number') ?>" class="input-text required-entry" value="<?php echo $this->escapeHtml($this->getInfoData('po_number')) ?>" />
</div>
</li>
<li>
<div class="<?php echo $this->getMethodCode() ?>-instructions-content agreement-content"><?php echo $this->__('your text here') ?>
</div>
</li>
</ul>
Make sure to add checkout-agreements to the ul class.