The first step is to download all your data from Coinbase Prime and upload it into Koinly. There are a couple of ways you can do that:
Note that if you want to import CSV files, you need 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 appear as Income on your final crypto tax documents!