Made some progress

db/migrate/20160221003621_create_follows.rb

@@ -0,0 +1,12 @@
+class CreateFollows < ActiveRecord::Migration
+  def change
+    create_table :follows do |t|
+      t.integer :account_id, null: false
+      t.integer :target_account_id, null: false
+
+      t.timestamps null: false
+    end
+
+    add_index :follows, [:account_id, :target_account_id], unique: true
+  end
+end