They announced the repayment program on their website and on Fb as well (maybe on other social media too). This was the initial statement: https://www.nicehash.com/blog/post/nicehash-will-fully-reimburse-its-users.

If you had an external wallet in the moment of the hack, in order to receive the funds paid monthly by them, you had to check that address that was affected during the hack. And in order to actually receive the funds in your external wallet, there should be at least 100.000 satoshis in order to make the payment (this is their minimum treshold for paying to external wallets). So if you had a small amount which never got to reach 100.000 satoshis, you have to mine on the old address to reach up to 100.000 satoshis (what you mine + what they paid) in order to actually receive your payment.

For internal wallets users things should have been way easier, as for internal wallets the minimum treshold is way lower. But, again, you must check the address you had during the hack.

It is all explained in the above link.

And if your 82% of the stolen funds (this is how much they paid back) is above the minimum treshold (100.000 satoshis for external wallet) and you still did not receive them, you can contact them on Fb. They respond usually in 1-3 days.

I hope this helps