You just have to import the extension from the TYPO3 network, install it, have all the required extensions (such as mh_lib, adodb, date2cal, ...) installed and you should be able to use it. Maybe you need to clear the cache (the one in typo3conf/) first.
In case you just see the spinner logo go round and round and round without anything happening check the following:
Delete all *.js files inside the typo3temp/ directory and reload the browser without caching (CTRL + F5) or even close and re-open it completely.
Check the source code of your website in order to find out if a file named typo3conf/ext/mh_lib/lib/js/class.mh_general.js or one called typo3conf/ext/mh_lib/lib/js/class.mh_general-compressed.js gets included. One of them is enough, which one just depends whether you're a debug user or not.→ In case it is not included, make sure that TYPO3 extensions are allowed to edit the HTML head part of your website. This should be done in your templates and is normally not a problem (normally you don't have to set anything).
Enable the 'Debug mode' inside the plug-in's backend (open the content element where you inserted mh_omsqlio, switch to the ADVANCED tab and enable 'Debug mode' → in case you are dealing with this manual, I suppose you must be at least some kind of administrator) and reload the frontend page where the plug-in is loaded.Instead of the table (or nothing) you should now get a relatively long debug output where primarily the top paragraph is interesting. It gives you the automatically produced SQL statement and a status message below where it says 'Result'. This is the most important row of all. What does it say?
Well, if it does not say 'Success – xx row(s)', I'm sure, something is wrong with the statement which means that something is wrong with the configuration in the backend which means that you should go on reading with the next part, 'Configuration'.If it does say 'Success – xx row(s)', maybe one of the callback functions returns a JavaScript producing error. Try disabling the callback function and have a look if it works then. If the error seams to appear inside the callback functions try step-by-step debugging. First return a fixed string like 'foo', then return something more dynamic and see, where the error appears. In case you have no clue, why it does not work, try addslashes($return) and str_replace(chr(10), '', $return) on your return (where $return is your return variable).
