1) Go to polkadot.js , click on "Network" and then "Staking".
Make sure you are connected to the SORA Network, you should see the logo at the top left.
2) Click on "Payouts".
If there is a staking reward for you to claim, you should see them, as in the picture below
3) Click on "Payout" and then follow the proposed flow.
Once completed, sign with the extension as proposed
Please note that unfortunately Polkadot.js supports only one asset for the network, that's why it shows XOR, but actually it's VAL (because polkadot.js supports only 1 asset).
Rewards expire after 84 eras. On SORA, that's about 21 days.
Important: when a nominator or the validator himself claim rewards, those are sent to all the accounts that have received a reward, so it is enough that one person claim for everyone. This may be the reason why you often don't see any reward in the website