With Joist, you can add an existing client from your Clients list to an estimate/invoice rather than having to re-enter the same client information over and over again.
1. Tap on Clients at the top of the screen
2. Tap the Green Circle with a "+" symbol in the bottom right corner
3. Tap on New Client, and here you can add the details for your new client
4. Tap the Green Checkmark in the top right corner to save