To add the new Author Signature app block to your theme has never been easier.
Use Application Deep Links
The easiest way to add the Signature app block to your default blog post template is to simply click on the deep link within the app.
Simply style to suit your theme and authors and then click 'Save'
Open the Theme Customisation menu
Select the Blog Post template you wish to add the Author Signature to
Click on 'Add block' if you have that option - alternatively use the 'Add section'
Click on the 'Author Signature' app block