The first step is to download all your data from Indodax and import them 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 all you have to do. Don't forget to tag your airdrops/forks so they show up as Income on your final crypto tax documents!