You don’t need services like buffer.com and dlvr.it to post your WordPress posts to Facebook and Twitter. Both costing around $10/month. You can do it for free using a plugin that you may already be using, Jetpack.
Here is how:

• Install the Jetpack WordPress plugin if you haven’t already.
• Go to ‘Jetpack’ > ‘settings’ in your WordPress dashboard menu.
• Click on ‘Publicize’ in your Jetpack dashboard menu.
• Setup your social accounts and save.
• You’re all ready to post!