This is a basic UI to help you convert back and forth between GNT and GNTW. MetaMask is the suggested client.
GNTW is a wrapper token for GNT that supports the full ERC-20 token standard.
The GNTW smart contract allows you to convert back and forth between GNT (Golem Network Token) and GNTW (Golem Network Token Wrapped).
The main benefit of converting to GNTW is that, since it supports the full ERC-20 token standard, you can trade GNTW on decentralized exchanges like EtherDelta.
Original source and discussion: on reddit.
Step 1: Generate personal deposit address.
Step 2: Send GNT to personal deposit address.
Step 3: Process deposit.