diff --git a/_apps/gpg.md b/_apps/gpg.md
index 15149df..ce3c835 100644
--- a/_apps/gpg.md
+++ b/_apps/gpg.md
@@ -4,6 +4,36 @@ description: Enforce GPG signatures on Pull Requests
 slug: probot-gpg
 screenshots:
 - https://user-images.githubusercontent.com/235875/30776187-bed103a8-a067-11e7-9ecc-5540c03114e1.png
+- https://user-images.githubusercontent.com/235875/30776885-3ab13158-a074-11e7-95df-8b6eb7d6b795.png
 authors: [ jarrodldavis ]
 repository: jarrodldavis/probot-gpg
 ---
+## Usage
+
+[Configure this app](https://github.com/apps/probot-gpg) on your organizations and repositories. Be sure to enable [required status checks](https://help.github.com/articles/about-required-status-checks/) if you want to enforce GPG signatures on all pull requests.
+
+## How it works
+
+Git supports [signing commits with GPG keys](https://git-scm.com/book/en/v2/Git-Tools-Signing-Your-Work) to verify commit authorship beyond the easy-to-forge [author](https://git-scm.com/docs/git-commit#git-commit---authorltauthorgt) field.
+
+GitHub supports [verifying GPG signatures on commits](https://github.com/blog/2144-gpg-signature-verification) and has an excellent [series of help articles](https://help.github.com/articles/signing-commits-with-gpg/) for creating a GPG key, using it with `git` locally, and linking it to your GitHub account.
+
+After installation, this app [checks all commits](https://developer.github.com/v3/repos/commits/#compare-two-commits) of new (or newly updated) pull requests for valid GPG signatures [according to the GitHub API](https://developer.github.com/changes/2016-04-04-git-signing-api-preview/). Note that for the status check to pass, _every_ contributor of a pull request must:
+- set up a GPG key on their local machine
+- sign _all_ of their commits in the pull request with that key
+- link that key with their GitHub account
+
+![GPG Status Check Success](https://user-images.githubusercontent.com/235875/30776187-bed103a8-a067-11e7-9ecc-5540c03114e1.png "GPG Status Check Success")
+
+Otherwise, the app will set the status to `failed`.
+
+![GPG Status Check Failed](https://user-images.githubusercontent.com/235875/30776885-3ab13158-a074-11e7-95df-8b6eb7d6b795.png "GPG Status Check Failed")
+
+## Further reading
+
+- [Git Tools - Signing Your Work](https://git-scm.com/book/en/v2/Git-Tools-Signing-Your-Work)
+- [GitHub Help: Signing commits with GPG](https://help.github.com/articles/signing-commits-with-gpg/)
+- [GitHub Help: Troubleshooting GPG](https://help.github.com/articles/troubleshooting-gpg/)
+- [GitHub Blog: GPG signature verification](https://github.com/blog/2144-gpg-signature-verification)
+- [GitHub Developer: Preview support for Git signing](https://developer.github.com/changes/2016-04-04-git-signing-api-preview/)
+- [The GNU Privacy Guard](https://gnupg.org)