How to auto-fill Posts (Posts Templates)

Hi,

I wanted to create a template for my posts to speed up posting.

Basically I just want some text to be auto populated in the post contents section when I click new post. So I can add to it or slightly tweak it.

I tried looking at the single.php file to see if there was any obvious place. But did not see anything that stood out.

Thank you so much for your help!!!