The first - and in most cases the only - step is to download all your data from Latoken and upload it to Koinly. There are a couple of ways you can do that:
Note that if you decide to use CSV files, you need to make sure to import your deposits/withdrawals and trades for ALL previous years - not just the current one!
That's it. The only other thing to keep in mind is to tag your airdrops/forks so they show up as Income on your final cryptocurrency tax reports!