Guidline needed for the Modification of Cardano Wallet for a Testnet Connectivity


I need to modify a cardano wallet for a given testnet environment. But I dont know how to start. Could you please give me some instruction or share me some tutorials. I am new in blockchain programming. Thus, I am getting difficulties.

If you know any modifiable/customizable wallet name, then please share the name of those wallet name too.

Thanks and regards,