The first - and in most cases, the only - step is to download all your transaction data from IDCM and upload it to Koinly. There are a few ways you can do that:
If you decide to use CSV files, you need to make sure to import your deposits/withdrawals and trades for ALL years !
That's it. Don't forget to tag your airdrops/forks so they show up as Income on your generated cryptocurrency tax forms!