What would be advisable to do before you claim BCH with ElectronCash wallet is to move your BTC from wallet where it is now.If you wonder why to do this answer is pretty simple.When you import your seed/private keys in any other wallet we can consider that it is no longer 100% safe.Some users download fake ElectronCash wallets and they lose BTC&BCH,it is better to ensure that this does not happen.

So to be 100% sure&safe,if you use Electrum(you should upgrade to 3.0.5 or above) you can create new wallet with File - New/Restore - Standard Wallet.Then from your old wallet send BTC to address in new wallet.When transaction is done and confirmed your BTC is safe and you can use your old seed/private keys to claim BCH or any other forked coin.

Use only these two links:

https://electrum.org/#home for Electrum

https://www.electroncash.org/ for ElectronCash