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AMS Module
I start here, you have some article, so install a block on the homepage from this module to show ex. the last articles. So you have content. So can choose as center block (in the middle) as one block from left to right or you can choose center left or center right block with 50percent of a center block, so you can make two block in one line, one left and one right. A lot of modules work on that way, that you can install a block to show content on every page on your website.
Images
You have the choice, choose the XOOPS internal image manager, here you can create many folders and give rights to the folders which group have access. There exist some picture moduls, ex. eXtGallery, TadGallery etc. here you have some more options with description and and and ...
YouTube Videos or Videos
The DHMTL Editor give you the option to link a YouTube Video, but search on this portal, you will find some video modules. With a little experience you can use another modules (ex. trabis dummy module) and in connection with a flash player (ex. JW Player) you can use your own style and ressource, all you need is now a download module, where user can upload video files to link in a website. Learning by Doing i will say...
Greets