To add yasnippets to your DOOM emacs you can add a directory named snippets to your DOOMDIR. The DOOMDIR is deafult set to ./.doom.d. Here you can add your snippets. Fx i have a snippet for org-mode that adds all relevant properties when i create a blog post. This snippet is named BlogPost, and has the following contents

# -*- mode: snippet -*-
# name: BlogPost
# uuid:
# key: blogpost
# condition: t
# --

#+DATE: `(format-time-string "%Y-%m-%dT%H:%m:%S.%3NZ")`
#+LANG: en

This is pretty basic, but one thing to note, and this is not a DOOM thing, but a yasnippet thing, i add a formatted date/time string when the snippet is activated. Now you can open a .org file and when you start writing blogpost, you will get a completion on the snippet, from a dropdown, when you pick it and press RET, the snippet is activated, the lisp code is run, and the result is inserted into your org document.