Export the private key corresponding to the funded address from your BTC-electrum
import this private key into a bitcoin cash wallet (depening on the wallet, a rescan might be needed)
Mark the BTC address in electrum as compromised, never use it again. It might even be wise to empty the BTC-electrum wallet and stop using it.
EDIT: i forgot: before exporting the private key for the deposit address from electrum, make sure there are no unspent outputs on the bitcoin network funding this address... If there are, it might be wise to spend these outputs on the bitcoin network before exporting the private key from electrum and importing it in an bitcoincash wallet... Bitcoincash wallets seem to be pretty secure, so the chance of them exposing the private keey are minimal, but it's better to be safe than sorry!
let me see that I understand :
1. In Electrum wallet : Wallet ->Private keys - > export
2. save the exported file on my desktop.
3. download a different wallet (BTC.com ? BU Bitcoin Cash Client?)?
4. import the whole keys to the new wallet ?
5. In Electrum wallet : Addresses->Right click -> Freeze
Am I right ? Am I missing something ?
Thank you !!!