From within your template, you can add an 'edit item' link by using this template variable. By default, it will link to a popup-bookmarklet-window, but that behaviour can be changed through the editlink template.
Note: only logged in members that are allowed to edit the item will see this link. In other cases, the edit-templatevar does nothing at all.
An example for the item body template
<h1><%title%></h1>
<p><%body%> <%morelink%></p>
<div class="metadata">
<%edit%> <%comments%>
</div>