It sounds easy. Publish on WordPress and see your post tweeted and posted on Facebook. I have used Facebook apps and WordPress plugins with some success, but eventually they were all disappointing me. They would miss some posts, post blank images, stop working completely (Facebook seems to change daily.).
I have SEO clients with blogs and the tie to social networks is very important and convenient.
NextScrips has finally given me one that works. I am only using it to post to Facebook and Twitter, but the plugin called, “Social Networks Auto Poster” allows your blog posts to immediately appear on Google+, Pinterest, and Tumbler also.
HINT: Follow the detailed instructions. You must setup up Apps on Twitter and Facebook. This is easier than it sounds, but follow the instructions.