To launch a wallet that has Stealth Mode enabled you must know the PIN code of the wallet or the alternative stealth PIN code you optionally defined.
Step 1 - Open the default phone dialer
Pretend you are making a phone call and open your phone dialer
Step 2 - Enter the launch code
And press the 'call' button. You won't actually be making any call so you don't have to worry about being charged by your network carrier.
Step 3 - Success
If the PIN code was correct then Samourai Wallet will launch. There will be no history of the launch code in your dialer history.