Step 1:
Click on Content Buckets

Step 2:
Click on Create Content Bucket

Step 3:
Give your new bucket a name and description.

From here you can upload your content via individual uploads or via a zip file upload.

Step 4:
To upload files in bulk, you will use the Zip File Option.
You will start by saving your graphics as png files and putting them into a folder on your desktop.

Step 5:
Then you will use the Simple CSV Sheet to add your file name, caption and first comment (for Facebook only). 
Step 6:
Add that CSV Sheet to your Folder with your Graphics

Step 7:
Compress or Zip that folder.

Step 8:
Click on the zip icon in the Content Bucket and upload that zipped file.
