diff --git a/slices/admin/actions/posts/add_syndication_source.rb b/slices/admin/actions/posts/add_syndication_source.rb
new file mode 100644
index 0000000..381f192
--- /dev/null
+++ b/slices/admin/actions/posts/add_syndication_source.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module Admin
+  module Actions
+    module Posts
+      class AddSyndicationSource < Admin::Action
+        include Deps["commands.posts.add_syndication_source"]
+
+        def handle(req, res)
+          add_syndication_source.call(post_id: req.params[:id],
+                                      source_name: req.params[:syndication_source_name],
+                                      source_url: req.params[:syndication_source_url]
+          )
+
+          res.status = 201
+          res.headers["HX-Refresh"] = true
+        end
+      end
+    end
+  end
+end
diff --git a/slices/admin/commands/posts/add_syndication_source.rb b/slices/admin/commands/posts/add_syndication_source.rb
new file mode 100644
index 0000000..985fc9b
--- /dev/null
+++ b/slices/admin/commands/posts/add_syndication_source.rb
@@ -0,0 +1,22 @@
+require "readability"
+require "down"
+
+module Admin
+  module Commands
+    module Posts
+      class AddSyndicationSource
+        include Dry::Monads[:result]
+        include Deps["repos.post_repo"]
+
+        def call(post_id:, source_name:, source_url:)
+          post = post_repo.find(id: post_id)
+          syndication_sources = post[:syndication_sources]
+          updated_syndication_sources = syndication_sources.merge(source_name => source_url)
+
+          post_repo.update(post_id, syndication_sources: updated_syndication_sources)
+          Success()
+        end
+      end
+    end
+  end
+end
diff --git a/slices/admin/config/routes.rb b/slices/admin/config/routes.rb
index daea836..a6f24ed 100644
--- a/slices/admin/config/routes.rb
+++ b/slices/admin/config/routes.rb
@@ -35,6 +35,7 @@ module Admin
     post "/posts/:id/archive", to: Auth.call(action: "posts.archive")
     post "/posts/:id/publish", to: Auth.call(action: "posts.publish")
     get "/posts/:id", to: Auth.call(action: "posts.show")
+    post "/posts/:id/syndicate/add_source", to: Auth.call(action: "posts.add_syndication_source")
     post "/posts/:id/syndicate/:target", to: Auth.call(action: "posts.syndicate")
     post "/post/:id/update", to: Auth.call(action: "posts.update")
 
diff --git a/slices/admin/templates/posts/show.html.slim b/slices/admin/templates/posts/show.html.slim
index e54b571..c1d481f 100644
--- a/slices/admin/templates/posts/show.html.slim
+++ b/slices/admin/templates/posts/show.html.slim
@@ -1,11 +1,23 @@
 
-div class="mb-12 prose dark:prose-invert max-w-prose mx-auto text-gray-800 dark:text-gray-200 bg-red-100"
+div class="mb-12 prose dark:prose-invert max-w-prose mx-auto text-gray-800 dark:text-gray-200 bg-pink-100 p-4 rounded"
   h3 Syndicated to
   ul
     - post.syndication_sources.to_a.each do |name, url|
      li
       a href=url
         = name
+  form hx-post="/admin/posts/#{post.id}/syndicate/add_source"
+    span class="mr-2"
+      label for="syndication_source_name"
+        ' Name:
+        select id="syndication_source_name" name="syndication_source_name"
+          option value="" (none)
+          option value="mastodon" Mastodon
+    span class="mr-2"
+      label for="syndication_source_url"
+        ' URL:
+        input type="text" id="syndication_source_url" name="syndication_source_url"
+    button type="submit" Add source
   button hx-post="/admin/posts/#{post.id}/syndicate/day_one" Send to Day One
 
 // TODO: Add preview, fix sending to DayOne