It looks like you have a good start already!
There are two ways to refer to a source multiple times. It doesn't matter if it is a link or not. First the link will be enclosed by brackets [ and ]. You'll put the url (http://www...) in and then skip a space and add how you want it to appear.
will show a link that looks like this:
You can use <ref></ref> tags to repeat the same source.
<ref name='wikitree'>[http://www.wikitree.com WikiTree]</ref>
This will put the little  in the text and list the WikiTree link below the Sources heading. Subsequent references to the same source are easy because all you need to type is <ref name=wikitree />
Personally, I use the <span></span> tags more. For that you will place the source link under the Sources heading and refer to it in the text.
== Sources ==
* <span id='wikitree'></span>[http://www.wikitree.com WikiTree]
Then in your text where you want to reference the source link, you'll type, <ref>[[#wikitree|WikiTree]]</ref> that will give you the .
For this style [[#type whatever you named the span tag]] Use the "|" pipe to tell it what you want to display. You could have also done
<ref>[[#wikitree|WikiTree, Where Genealogists Collaborate]]</ref> will look like this:
1. WikiTree, Where Genealogists Collaborate
and link to your source link.
This is really easier than it seems. You just need a little practice.