The first and usually only step is to download all your transactions from Fatbtc and upload them into Koinly. There are a couple of ways you can do that:
If you decide to import CSV files, you need to make sure to import your deposits/withdrawals and trades for ALL previous years - not just the current one!
That's all you have to do. The only other thing to keep in mind is to tag your airdrops/forks so they show up as Income on your final cryptocurrency tax forms!