You don’t need a wordpress plugin to add photos/picture as attachment. All you have to do is just click the icon “Add an image“, which you can see near to your title box while writing new or editing an old post.
After image has been uploaded, you can add titles, caption and descriptions.
Click Insert into post button to add the uploaded picture into your post. Also this window will allow to set the size ( thumbnail, medium, large, or full size) and alignment to your image.
If you don’t see “Add an image” in your current wordpress admin page, you could be running an older version of wordpress, so upgrade your wordpress to latest version.