Two users to one person are not allowed by WGT's T&Cs, and they may become very strict in locking them up.
My advice is to chose the more "valuable" of them and to silently abandon the other one - just don't touch it any more (no play, no actions between the accounts!) and to use the chosen one exclusively(!!), on any device you want.
Usually, you should be able to log in with the same username and password on any PC or tablet, after installing the appropriate app.
Log-ins by browser (www.wgt.com) should also be possible but don't allow you to play the game.