The first step is to download all your transaction data from GuldenTrader and upload them to Koinly. There are a few ways you can do this:
If you decide 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. Don't forget to tag your airdrops/forks so they appear as Income on your final cryptocurrency tax reports!