Abra currently supports cryptocurrency deposits using bitcoin. You can do this by tapping “Send or receive” in the app, then selecting “Bitcoin”. You should then see your Abra wallet address, which you can scan as a QR code, or copy the address as text. Use this address to send your existing bitcoin into Abra.
At this time it is not possible to deposit cryptocurrencies other than bitcoin into Abra.
Some customers sell their other cryptocurrencies for bitcoin so they can bring it all under one app with Abra. To do this, these customers will use an exchange or a conversion service such as ShapeShift or Changelly to get the bitcoin into Abra.