The first - and in most cases, the only - step is to download all your transaction data from Samourai Wallet and import it into Koinly. There are a couple of ways you can do this:
Note that if you want to import CSV files, you must make sure to import your deposits/withdrawals and trades for ALL years - not just the current one!
That's pretty much it. The only other thing to keep in mind is to tag your airdrops/forks so they appear as Income on your generated cryptocurrency tax documents!