The first - and in most cases, the only - step is to download all your data from Blockchains.my and upload them into Koinly. There are a couple of ways you can do this:
Note that if you want to import CSV files, you must make sure to import your deposits/withdrawals and trades for ALL previous years !
That's pretty much it. Don't forget to tag your airdrops/forks so they show up as Income on your generated cryptocurrency tax documents!