The first - and in most cases, the only - step is to download all your transaction data from Alterdice and import it to Koinly. There are a few ways you can do this:
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 all you have to do. Don't forget to tag your airdrops/forks so they appear as Income on your final crypto tax documents!