Flesh out welcome section

Author: hollenberry

responses/welcome.md

@@ -1,6 +1,14 @@
-Welcome. There's some boilerplate in your Code tab which contains most of what you need to get your Learning Lab course up and running.
+# Welcome!
 
-However, we need to fill in some of the fields. I've started a branch with the first changes.
+If you look around this repository, you'll find a few standard template files in your Code tab which contains most of what you need to get a Learning Lab course up and running.
+
+However, we need to fill in some of the missing fields. To kick things off, I've started a branch with the first changes.
+
+### New to GitHub?
+
+For this course, you'll need to know how to create a branch on GitHub, commit changes using Git, and open a pull request on GitHub. If you need a refresher on the GitHub flow, check out [the Introduction to GitHub course]({{ host}}/courses/introduction-to-github).
+
+You'll also need a broad understanding of webhooks and the GitHub API, which are covered in [the Getting started with GitHub Apps course]({{ host}}/courses/getting-started-with-github-apps),
 
 ### :keyboard: Activity: Open a PR