Newspread 1.0.4+ supports Jetpack integration for a number of features. Install it if you have not already.

1. Install the Plugin

Go to Plugins, search for Jetpack - then install and activate it.

You will need to register with (free) and connect your site to the account. Basic Jetpack usage is free.

2. Activate Related Posts

Go to Jetpack > Settings and search for 'infinite'.

Set it up like the screenshot below - loading them with a button.