Currently Mirror Wallet supports 3 methods of funding:
Depositing UST by sending UST to the wallet address
Purchasing UST using credit cards through a 3rd-party service provided by MoonPay
Depositing Luna and converting to UST
Funds from the wallet can be withdrawn by sending UST to external addresses.
If you have any available Luna tokens in your wallet, you can convert Luna tokens to UST before withdrawing to an external address.