add install instructions

README.md

@@ -1,4 +1,15 @@
 NoShorts
 ========
 
-This is a FireFox extension that redirects any YouTube shorts URLs to use the regular YouTube video player.
+This is a Firefox extension that redirects any YouTube shorts URLs to use the regular YouTube video player.
+
+## Temporary Installation Instructions
+
+1. Navigate to [about:debugging](about:debugging) in Firefox.
+2. Click "This Firefox" on the left sidebar.
+3. Click "Load Temporary Add-on...".
+4. Navigate to and select [./noshorts/manifest.json](./noshorts/manifest.json)
+
+## Permanent Install Instructions
+
+This extension isn't published and signed, so you have to disable the add-on signature check to install it permanently. Not recommended!