The first - and in most cases the only - step is to download all your transactions from Bithesap and import it into Koinly. There are a couple of ways you can do that:
If you want to use 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 appear as Income on your final crypto tax forms!