diff --git a/README.md b/README.md
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@@ -1,5 +1,17 @@
 # NetSigil
 
-Sign an entire [Website]/[Gemini capsule]/[Gopher hole]
-
-Verify any file on a signed [Website]/[Gemini capsule]/[Gopher hole]
\ No newline at end of file
+* Sign an entire [Website]/[Gemini capsule]/[Gopher hole]
+* Verify any file on a signed [Website]/[Gemini capsule]/[Gopher hole]
+
+Uses [signify](https://www.openbsd.org/papers/bsdcan-signify.html).  GPG support might be added later.
+
+Generates `.well-known/signature-bundle`, a signed tar.gz file.
+
+Explained here: https://lists.orbitalfox.eu/archives/gemini/2021/005585.html
+
+Usage:
+
+```
+netsigil --sign <dir>    # Sign a local copy of your site
+netsigil --verify <URL>  # Verify remote signature
+```