Hi Jayasankar,
Based on the mentioned case, you will have to
1) Add a custom class (with a space/blank after the default class) to the popup widget Style Classes property as shown below.
Ex: custom-popup-style
2) Add a class definition to the respective Screen Style Sheet section as mentioned below
.custom-popup-style {
min-width: 70%;
}
Hope this helps you!
Kind regards,
Benjith Sam