They all are a little different. It seems that anything is traded in a pair with BTC. So it you select that pair first then in the trading window you should be able to quickly trade from BTC to chosen coin. Or trade out of held coin to BTC and then select the new coin pair with BTC. The process is what got me converted to the idea that the game is to accumulate as much BTC as possible and to really think in terms of BTC as what your holdings are worth and not USD.
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