In order to trade there, you must have cryptocurrency to begin with.
The only asset class you can deposit to Azbit is cryptocurrency.
However, if you really like Azbit but you don’t have any crypto yet, you can easily start an account with an exchange that has “fiat on-ramps” (an exchange where you can deposit regular cash), buy crypto there, and then transfer it from such exchange to this exchange. Something like ATAIX or others.