1. Tap the create new  icon in the bottom of the screen.
   
2. Choose Templates . This will open the list of templates categories.
   
   
   
   
   
   
3. To select your template, tap the preferred template thumbnail and tap the check mark icon at the top- right corner of the screen. 
   
   
   

You can also double-tap your preferred template thumbnail to select it.

1. Tap the New Slide  icon in the bottom-right corner. By default, this will open with the layout options.
   
   
   
   
   
   
2. Tap to select your preferred layout from the standard layouts or slide layouts to add it as a new slide.
   
   
   
   
   

You can view all the slides of the templates at the bottom of the screen as thumbnails.

1. Tap the New Slide  icon in the bottom-right corner. 
2. Select Gallery in the top. 
   
   
   
   
   
3. Tap to select any slide from the slide design options to add as a new slide. 
   
   
   

It is not mandatory to use all the slides in a template. You can add or delete slides according to your requirement.

Also read: Create presentations with themes