Iam already installed electrum wallet on laptop , how to use testnet
For the MacOS version of Electrum Testnet, type the following command line in Terminal (assuming the Electrum application you are using is in the default Applications folder):
open -n /Applications/Electrum.app --args --testnet
-snip-
For Electrum testnet on Windows OS:
Right-click the Electrum shortcut; In the Properties-Shortcut, edit the Target column by adding the following text at the end:
--testnet

