You can get a good view of how the cap comes on and off if you look at the videos included in the sticky at the top of this forum (Getting Started With Spin Tops).
There isn’t really any great reason to open it until you have a problem or get good enough to worry about trying to balance it. It is more important to tape it and get your throw down. After your top takes a few hard hits, the cap will probably loosen up anyways.
If you are determined to get into it, try using something that will give you a better grip on the cap, like something you use for opening stubborn jar lids. Also, push down a little as you turn the cap counter clockwise.
Check out the sticky, it is one of the best resources that exists for getting started with a Bearing King.