In WordPress Dashboard go to Appearance submenu and click on Customize.
After clicking on customizing you will in theme Customizer.
Here you have to click on Page Template than Portfolio Page
In Setting, Here you can Hide / Show Portfolio & Newsletter .
Go to Customize -> Page Template -> Portfolio Page -> Setting
In WordPress Dashboard go to Appearance submenu and click on Customize.
After clicking on customizing you will in theme Customizer.
Here you have to click on Page Template than Portfolio Page
In Content, Here you According to Display Content .
Go to Customize -> Page Template -> Portfolio Page -> Content
You have to use Portfolio Image Size 540Px X 372Px