I purchased new balls and I cannot get at them to play. Also, when do I get more credits? I got 100 when I started but never seem to get any more and I'm using up the ones I had.
You need to equip anything you buy in order to use it.
How to Equip Your Bag
To attain more credits you must advance your tier, place in the top 70 in tournaments or just buy them @ 100 credits per dollar. Have a look at this:
Deposits & Credits