I bought one of those earlier this year (its originally what sucked me in to CPs). After a bit of research, I realized this was a mistake and tried to cancel the order, but it had already shipped. Instead of losing ten bucks to ship it back, I decided to give it a shot.
I can't say how succesful my attempt will be at this point, but I stared off by ignoring the terrarium and placing all of my seeds into a distilled-water-moistened paper towel and placing that in a small plastic bag, which I then placed in the refrigerator(saves space and from what I hear is just about as affective). If you choose to do this, leave a bit of air in the bag and check it every week or two for mold.
The problem with this kit is, as stated above, the seeds are probably old and not terribly viable. Another problem is that all the plants included are "outside" plants(they can be grown successfully inside in some cases, but best results for a beginner are oustide) and many of them grow to be quite large(much too large for the tiny terrarium). A third problem is that, after the seeds have germinated and the seedlings have begun to grow, you do not need the terrarium lid...that much humidity is simply not necessary; at least not in Alabama.
Anyways, I'm still a beginner my own self, so please don't think I'm talking down at you. Best of Luck and welcome to the forums!