The first - and in most cases the only - step is to download all your transactions from Changelly and import it to Koinly. There are a few ways you can do that:
Note that if you want to import CSV files, you have to make sure to import your deposits/withdrawals and trades for ALL previous years !
That's all you have to do. The only other thing to be vary of is to tag your airdrops/forks so they show up as Income on your generated crypto tax forms!