There are 2 ways to restore your wallet:

1. With a 12-word mnemonic phrase

Using an app

• if you haven't logged in yet, just tap on "Import existing wallet" and enter your mnemonic.
• If you are logged in, you need to logout (go to sidebar in the top right corner and pick "Log out"), then tap on "Import existing wallet" and enter your mnemonic

Using web version:

Go to web.lumiwallet.com, click on "import wallet", pick Option 1 and enter your mnemonic.

2. With a wallet file (available only in the web version)

Go to web.lumiwallet.com, click on "import wallet", pick Option 2, upload your wallet file and enter your wallet password.