The first and usually the only step is to download all your transaction data from CODEX Exchange and upload it into Koinly. There are a couple of ways you can do that:
If you decide to import CSV files, you have to make sure to import your deposits/withdrawals and trades for ALL previous years - not just the current one!
That's pretty much it. Don't forget to tag your airdrops/forks so they appear as Income on your generated crypto tax forms!