How to trade BCC with Blockchain app and private key There is something I do not understand.

I have handled a few bitcoin transactions using Android Blockchain app and imported private key. That worked and could buy/sell with btcdirect.eu (start transaction with btcdirect.eu and exchange bitcoin with Blockchain app)

Now after the hard fork I want to see my BCC and buy more of it, but how can I do that with my private key? If possible I want to use the Blockchain app.
In case you have your private key (or the memnomics) you can use the BIP39 browser at https://iancoleman.github.io/bip39/ to see the funds in your internal and external addresses.

More info on how to at How to sweep private extended key from mycellium into coinomi for bitcoin cash coins?