You can upload images and files by going to "Manage Images and Files".

Next Click on the Folder you wish to upload your images to on the left or create a new folder.

Then click on "upload new files"

Next click select the files from your computer ( you can choose multiple files at a time)

Click on "open" after selecting multiple files (NOTE: you can hold down SHIFT or CTRL to select multiple files)

Next click the "Upload" button and watch the dialog box move accross your screen.