Update January 2021: Please note that ADX farming finished on 28.12.2020!
When you interact with farming on the Staking Portal, you must first approve an address. This is your staking identity address.
If you haven't used your wallet for staking before the address seem strange, as it has no activity. If you have used your wallet on the staking portal previously, you'd be able to see the activity from staking before.
You can verify whether you are approving the correct address by comparing it to your gasless account address. The addresses must be the same.
Here's how to see your gassless account address:
Step 1: Connect your wallet to the staking portal.
Step 2: Click on Gasless Staking in the menu on the left:
Step 3: Make sure the address you're approving is the same as the address shown in the page.