The first - and in most cases, the only - step is to download all your transaction data from Tidex and upload them to Koinly. There are a couple of ways you can do this:
If you decide to import 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 all you have to do. The only other thing to keep in mind is to tag your airdrops/forks so they appear as Income on your generated cryptocurrency tax documents!