How do you send ETH from a wallet contract using the Parity Wallet?
I tried selecting the wallet contract, and selected execute contract but I didn't see an option to send ETH to another address.
The Parity team has taken the time to write incredible documentation about their wallet. You will not only find the answer to your problem, but to many future ones you may have. Take a look at the docs for your solution.
For your specific question, follow the logical steps in the GUI. Specifically:
1) Open the GUI
2) Click on the "Accounts Management" tab
3) Click "Transfer". You will see this screen:
4) Enter the recipient's address, the amount you want to send, and then press send. Type in password.