The description seems to be the same as the last Astak firmware update. If the current page in your ePub has a hyperlink, pressing the zero key will highlight (underline) the hyperlink and you would press the ok button to follow it. If there is more than one hyperlink on a page, you just keep pressing the zero key until the hyperlink you want to follow is highlighted, pressing 9 will highlight the previous hyperlink. In JSWolf's example, to choose hyperlink 15, you would press the zero button 15 times and then hit the ok button.
Unfortunately, there isn't a 'back' command in the epub format once you follow a hyperlink, so you'll need to bookmark the page or check to see what page number you are on so you'll know where to return to. If this is actually a new firmware update, hopefully they've corrected this.
(Hyperlinks in the mobi format work differently and there is a way to return to your original spot in the book.)