Enable push / slide menu button in header
POFO has options not only to push / slide menu button in header globally but also you can set it on single page/post/portfolio level.
Push / slide menu button in header globally for whole website
Please refer this article for more inforamtion Theme Customizer > Main-Header >Header Style And Data
Push / slide menu button in header page / post / portfolio level
Please follow below simple steps.
Step 1: Go to WordPress Admin > Add/Edit page/post/portfolio
Step 2: Find POFO page / post / portfolio settings > Header > Header style and data.
Step 3: You can select Slide Menu on/off and also select slide menu sidebar to display in slide sidebar. Please check below image for information.
Screenshot after clicked slide menu button.