An automation in Personal Discount needs a Cart Price Rule to which it will be adding coupon codes.
You can prepare a Cart Price Rule in your Magento admin panel.
Navigate to Marketing > Cart Price Rules and click on Add New Rule.
Cart Price Rules in Magento provide a variety of options. The essential ones are:
Rule Name - will appear on the select list in Personal Discount
Active - yes
Websites - select all, unless you want to limit the coupon to specific website
Customer Groups - select all, unless you want to limit the coupon to a specific customer group
Coupon - Specific Coupon
Use Auto Generation - checked, this is key for Personal Discount to work properly
Uses per Coupon - how many times a customer can use a coupon code
Apply - discount type, possible choices are:
Percent of product price discount
Fixed amount discount
Fixed amount discount for whole cart
Buy X get Y
Save the Price Rule and switch to Personal Discount automation settings. Now, you can select the newly created "Welcome 10% off" as a Cart price rule for your automation.
The automation will start adding coupon codes to the selected Price Rule. You can find the generated coupons in the Manage Coupon Codes section of your Cart Price Rule: