Hello there, Aura Design.

We cannot directly apply a deposit to an estimate. Instead, you'll need to convert the estimate to an invoice. Then, you can add the deposit amount. Here's how:

1. Open the estimate and click the Create invoice button.
   
2. In the Invoice page, click the Gear icon in the upper-right corner.
3. Under the Customize what you see here section, mark the Deposit box.
   
4. At the lower right of the Invoice page, enter the deposit amount in the Deposit field.
   
5. Click Save and close.

You can also use this article to know more about estimates and invoices:

• Set Up and Use Estimates and Quotes
• How to Create an Invoice

I'll be around if you have more questions about this.