how do you use social media such as blogging, facebook etc..?

I am having some trouble understanding how to use social media such as facebook to promote my photography business. Right now, when I completed a project, I would write a blog post and share the post onto my facebook business page. However I can't tag anyone on the shared post. So I end up uploading the same images to the facebook page and do tagging there. Sounds pretty dumb but I can't find another way to do tag people. Perhaps I am missing something? I am using word press, and I see some website's blog contains a facebook comment section. Does anyone what plugin was used?

"Business" / Fan pages can only tag other business / fan pages.

It is confusing, but the way to tag people is to first friend them with your personal account. If this personal account is the admin of your business page, then that connection allows you to tag. You can also post items as your business page or as your personal page.
The above is for photo tagging. If you want to tag people within text or links only, I've never tried that.

You use social media presence to gain more links & visitors back to your own website. For example if you just have only your website as your online presence that will be only one way for people to find you and your services. By having FB page & other social media accounts you are creating new places where you & your services can be found by potential clients. By posting post after post you are creating additional advertisements for you & your services.