I've taken the liberty to find out how it works so I hope this helps...
First create a directory where you want your database to be stored (ie. c:\Program Files\Maple 12\AddedHelpFiles)
Now in order for maple to use it and read it everytime you start maple instead of having to invoke it using the libname command for each session you want to access your help file, create a Maple.ini file in your c:\Program Files\Maple12 directory using notepad and include the line (for our example) libname:=`c:/ProgramFiles/Maple12/AddedHelpFiles`,libname: the colon will supress the output when maple loads and your new directory and help pages will be included in your following new maple sessions. Note: be careful of the direction of the slashes, using the other slashes will give you an error.
Next open a worksheet and create a page you want added to the help database. Then go to Tools->Help Database-> Save as help page.
Under select Writeable database enter your newly created directory c:\ProgramFiles\Maple12/AddedHelpFiles\Maple.hdb (You can call you help database file whatever you wish, I've just named it Maple.hdb for convenience) Also note the direction of the slashes, again I cannot tell you why but that's the way maple shows them in it's list of writeable database files so I've just followed the same convention.
Under Topic, enter the searchable name you want. We'll call it, Helptopic. So whenever you search, it will pull up your help page. Also note to keep this name the same as the name you will put for your table of contents name or you will never be able to remove it from your database when they differ if you forget.
Now the tricky part is that the Table of Contents entry is optional, unfortunately if you don't enter anything here you will have much difficulty if at all finding your page while browsing the help database except by using ?Helptopic to find it. Your help page will be put somewhere by Maple in which I have had no luck in finding.
For our example we'll enter the same as we put for our Topic entry, Helptopic. So this help page will now be put in the help page under the name we entered here. However most people likely will probably want the pages to be under a subdirectory name. To do this you must enter a slash "/" after the name in the directory you want but don't forget to name the help page for the table of contents or it will be nameless. So for our example we'll type in Helptopic/Helptopic and our help page will now be named Helptopic under the directory name Helptopic searchable by the name Helptopic from our entry we put in for the Topic field. Confusing, eh?
Well we're done. Then we just click okay and a box pops up The worksheet may contain features which are not compatible with the chosen format. Continue? Just ignore and click okay and the next box that pops up is The database c:\ProgramFiles\Maple12/AddedHelpFilesMaple.hdb does not exist. Do you want to create it? Just click yes. And there you go.
There's a bug where there's a missing slash in the pop-up box but it's not critical.
Close maple and restart or invoke the libname command in your current maple session in order to use your maple help pages.