You can delete your Wickr Me account from within the app. You will have to be able to login to the app in order to delete your account, and there is no way to delete an account without the current working password.
On iOS, you can go to Settings -> Terminate Account as shown below:
On Android, you'll do the same. Settings -> Terminate Account:
On Windows and macOS, you'll tap the Settings menu next to your avatar, and then select Terminate Account: