First, click the “Add Media” button above the Visual Editor:
Then upload your images:
Or, to create a gallery, click on “Create Gallery” on the left side of the window, and then select the images you wish to include:
Then, click on the Create a new gallery button in the bottom, right hand corner of the Media Manager:
If you love video, you can also embed videos on your blog from supported services, such as YouTube and Vimeo. Copy and paste the URL from your address bar — on its own line — into your post, publish the post, and you’re done!
Or, with the VideoPress feature, included with the WordPress.com Premium and WordPress.com Business plans, you can upload your own videos directly to your blog with the Add Media button — just like adding photos.