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The top menu will suit you because you will need to change the links in the theme.html in the 7DanaRed theme folder manually.
For the side menu (well you can also make the top menu as well) with Multi-Menu, check the link below ;o)
Multi Menu <<< this is the original news item, worth a read?
Latest version 1.8 This is from the comments, stating an update.
There should be a side menu already but multi menu is a module in fact an excellent module for creating menus the way you want them. In this case Multi menu will replace the standard side menu, this will also involve learning about the blocks that XOOPS uses, eg. you will have to turn some off and turn the multi menu blocks you create to on or visible,
Anyway have a look at it and see how you go.
For html pages within XOOPS you can look at the content module, Article 1.0 News module maybe, there is quite a few then you can link to the page you make with multi menu if you like. So you could create an about us page in one of the modules I mentioned and just link to individual pages within that module if you like. I am sure others may have other ideas and have personal preferences for the module best equipped to handle this.
Cheers......;o)