If you want to set up your product pages and box overview pages you need to upload the images of brands and brand teasers in order to associate them to the products and brands later on.
Notice: You can't upload product images via media uploader,. This can be done in "catalog/manage products → images" section

Step 1:

Go to Beautytrends → GMS Manager → Media Uploader

Step 2:

Browse for the images on your computer and upload them to Magento!

You can select multiple images and upload them at once! You will see the green boxes with the name of the image you just uploaded once the file has been uploaded successfully.