Hi Narda,

I'm not quite get you here.Correct me if I'm wrong here, do you mean, you want to add and attachment in your blog post?
If yes, you can do it by:
[If you using built-in composer]
1. Open the composer>Add Blocks>File
refer this: http://screencast.com/t/7lKGYYvd http://screencast.com/t/tx3ag4wD