The first - and in most cases the only - step is to download all your transaction data from Mobi and upload it into Koinly. There are a couple of ways you can do that:
If you want to import CSV files, you have to make sure to import your deposits/withdrawals and trades for ALL years - not just the current one!
That's all you have to do. The only other thing to be vary of is to tag your airdrops/forks so they show up as Income on your final cryptocurrency tax documents!