Links in the main menu are related to installed modules. To remove a link go to system admin/modules and change the "1" to "0" in the order field.
To add links to the main menu is a bit more complex see this thread here
https://xoops.org/modules/newbb/viewtopic.php?viewmode=flat&topic_id=14480&forum=202 In system admin/blocks you can add your own custom blocks using HTML or text--and set up a custom block say using the center block-center option. Specifying that the block appears on the "top page" means the block will only be visible on the "start page". The "top page" is whatever module you have set up to launch at default i.e. "News". If you have no default module set up in general preferences, then the block will appear on the first page launched--or any other modules you choose to have the block appear in.
You use the "weight" option to determine which block appears first in the list, ie. 1,2,3 etc
3. For including content XOOPS comes with a basic "sections module", but this is depreciated, many other content modules have been designed for Xoops:
Wfsections, Soapbox, Tinycontent, Cjaycontent, Articles, Freecontent etc. Most of them have global search included
Try doing a search using the above names.
Static pages can also be included in Xoops, but these will not be included in the XOOPS global search
See the Wiki Home link to the right, there is an article about static pages and content.
I have a bug fix version of wfsections for download at my site. Soapbox is also very good popular recent addition, but the blocks that come with the module are causing problems which is being addressed
Edit: someone beat me too it, waste of time, see the above..