MailFirst Newsletter plugin provides you the option to display the popup type Optin form as per your need and desire. There are multiple of the options from which you can choose when to display the popup to the user and also you can specify where you want to display the popup to the user.
To change the Optin form styles go to Newsletter > Edit Newsletter > Display
On Site Open
In order to display the popup when user open the site
Delay in Sec
If the on site open option is selected then you can specify the no of seconds after which the popup will display when user visit the site
On Site Leave
In order to display the popup when user cursor goes outside of the site screen
On Page Scroll
In order to display when user is scrolling the page or site
Scroll Percentage
If the on page scroll option is enable then you can specify the percentage of screen after scroll on which the popup will appear
Close After Subscribe
In order to hide the popup if user is subscribed to the newsletter
Display Options
This option enables you to specify the part of site that on which page you want the popup to be appear
Note: This Display options are only valid for the Popup type Optin form