The first - and in most cases, the only - step is to download all your transactions from Dcoin and import them into Koinly. There are a few ways you can do this:
If you want to use CSV files, you must make sure to import your deposits/withdrawals and trades for ALL years - not just the current one!
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 final cryptocurrency tax documents!