Go to the Design Studioarea
Under New, click Upload Image or File.
Select the folder where you want to store the images or files, then click Browse.
To add multiple images and files, browse to the correct folder on your computer, press Ctrl/Cmd and click on each file you want to add,and
then click Open.
Expand the File Details to verify you selected the correct images, then click Upload.
When the upload completes, click Finish.
Your images are now available to use in campaign emails and landing pages.