How do I delete my current wallet and start over?
You can erase your current wallet in Sia-UI. Doing so generates a new wallet with a new 29-word seed. This is not recommended if you currently have Siacoin in your wallet. Any Siacoin in your current wallet will not be destroyed, but will no longer be accessible unless you restore from your previous seed.
To delete your current wallet, go to the Terminal tab and type:
wallet init --force
This will immediately create a new wallet and seed. The new seed can be used to unlock your wallet.