So your question may be how to find the prior answers. Here's what I used:
That seems to find that a plugin may be required or maybe a bit of code on your part.
The video at https://www.youtube.com/watch?v=iXNv14RmlMk seems to be a step by step as well.
Hi! Hello everybody! I'm using joomla. I have a CMS Joomla. I need to create pop-up windows in the center of the site! How can I create? I was looking for a plugin on the subject, but I can not find! So I want to create this plagin. How I can create this plugin? If you have this plugin, please let me or give, how can I find it? \\ For example
If you don't understand me ! Look at the picture...
Jommla CMS establishment in the center of the box?