The first, and in most cases the only, step is to download all your data from Coinhub and upload them 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 keep in mind is to tag your airdrops/forks so they show up as Income on your generated cryptocurrency tax forms!