The type of Off Canvas you want for a push menu is a Sliding Bar. So the first thing to do is to go to Avada > Off Canvas, and create your Off Canvas. Give it a name, and change the type to Sliding Bar.
You will need to configure the Off Canvas as you require, but the main settings you need to make a Push Menu is to make the Off Canvas a Sliding Bar, and to set the Push Transition option.
You might also want to turn off the Close Button option on the Close tab, as a Push menu would typically be toggled from the main menu in the header. For that reason, you don’t need any Conditions or Triggers for a Push Menu Off Canvas.