When you create a new page in the existing diagram, you can insert a template by clicking Arrange, Insert, Template... (or the + icon in the toolbar and Template...).

To insert a file from any URL (eg. the example diagrams in our drawio-diagrams repository), use the following steps:

1. Find a template you would like to add in https://github.com/jgraph/drawio-diagrams

2. Click File > Import from > URL in draw.io

3. Paste the template link into URL field  

4. Click the "Import" button

For example, if you want to add diagrams/bulb.xml, you should paste https://jgraph.github.io/drawio-diagrams/diagrams/bulb.xml

Additional info can be found here.

It is the same procedure for all diagrams in our drawio-diagrams repository.