[Kestryll]

I have to admit, this is going a bit beyond my scope of knowledge and I'm a bit lost.

I'm trying to place the same rotating banner ads in 4.2.2 that I currently use in 3.8.7
I've been told I need to register the templates and have been directed to this thread.
I am certain the answer is here however I'm not grasping it.

I currently run in house advertising via a table in the header that calls to plugins using the PHP random feature like this:
In Table in header:

<td style="width: 120px; text-align: center; height: 60px;">$random_banner12[$random_number12]</td>

In plug ins with a hook location of 'parse_templates' Execution order 5

$random_number12 = rand(1, 3);

$random_banner12[1] = '<a href="http://www.vendor/" target="_blank"><img src="/images/ads12/vendor.gif" alt="" border="0" /></a>';

I'm not sure which of these needs to be registered or where to do that at.
Any help would be appreciated.