The first and usually the only step is to download all your transaction data from purse.io and import them to Koinly. There are a few ways you can do that:
Note that if you want to use CSV files, you need to make sure to import your deposits/withdrawals and trades for ALL previous years and not just the current one!
That's pretty much it. The only other thing to be vary of is to tag your airdrops/forks so they appear as Income on your generated cryptocurrency tax forms!