The first - and in most cases the only - step is to download all your data from bcex and import them into Koinly. There are a few ways you can do that:
Note that if you decide to import CSV files, you must make sure to import your deposits/withdrawals and trades for ALL years and 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 final crypto tax forms!