The first and usually the only step is to download all your transactions from DDEX and import it into Koinly. There are a couple of ways you can do that:
Note that if you want to import CSV files, you have to make sure to import your deposits/withdrawals and trades for ALL years and not just the current one!
That's all you have to do. Don't forget to tag your airdrops/forks so they appear as Income on your final crypto tax documents!