If you have had your coins from before the hard fork that gave us Bitcoin Cash, you have the same amount in Bitcoin Cash (BCH).
Otherwise you'd have to exchange your BTC for BCC and transfer that as payment.
Yes I have the coins before the fork but the value in dollars for each one is different, bitmain is asking for more than 4 BCC, in BTC will be less than one BTC.
I don't see any other way than open a BCC wallet and transfer from the BTC wallet.
Yeah, the value is quite different and BCH is quite under pressure, pricewise, both because people are mining and instant selling, and because it's not really interesting enough for a lot of people to hold, because potentially all BTC holders could liquidate all the BCH they got for free with the fork.
You'll need to add your private keys for your BTC wallet in a BCH wallet to get the BCH there. Which of course is a risk, but that's well documented on the forum.