The first step is to download all your transaction data from DX.Exchange and import it into Koinly. There are a few ways you can do that:
If you want to use CSV files, you must make sure to import your deposits/withdrawals and trades for ALL previous years - not just the current one!
That's all you have to do. The only other thing to be vary of is to tag your airdrops/forks so they appear as Income on your final cryptocurrency tax forms!