The first step is to download all your transaction data from Coinall and import them into Koinly. There are a few ways you can do this:
Note that if you want to import CSV files, you have 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 show up as Income on your generated crypto tax documents!