Congratualtions on your new Kegelmaster! I'm sure you will learn to love it!
It does sound like you are not using it quite correctly. you shouldn't have to use your abdominal muscles for a correct kegel.
Are you using the 2nd device to help locate 'those' muscles?
Are you doing it nice and slow, like an 'elevator' slowly moving up? And are you starting with just one spring?
It could be that its too easy on one spring and you'll need to move up, OR you are tensing everywhere.
Try going slow, and only using the same muscles that make you stop urinating.
Also, give it some time. Usually it will take a couple weeks to feel a difference... just like with working any muscle, slow and steady wins the race.