Click on Content from the left sidebar.
Click on Your Buckets
Click on Create Content Bucket
Give your Bucket a Name and Description.
Now you can upload an individual post by click on Choose File under Individual Image.
You also have the option to upload a zipped package if you have several posts you would like to upload at one time. You can do that by clicking on Add Zipped Package.
If you choose to upload several images at once using the zipped package upload you will need to do the following.