This is pretty simple, but still worth mentioning.

In order to add the green content markers to your page in XSLT, use this

As for .NET, you have a number of options:

This will create the content marker that points to the context item: <sc:ContentDot id="contentDot" runat="server" />

This will create the content marker that points to the “news” item: <sc:ContentDot id="contentDot" DataSource="/sitecore/content/home/news" runat="server" />

This will create the content marker that points to the item with the specified ID: <sc:ContentDot id="contentDot" DataSource="{687BF9D7-9968-4EDF-863E-0A2611DDD51B}" runat="server" />

If you are constructing the controls dynamically, here