There is a couple of ways to upload images.
1. Go to Media library and click the blue “Upload” button on the left. You can then drag the files right to the admin interface from your computer or use the upload button. When files are uploaded, a pop-up window appears, in which you can select to what album(s) to add the uploaded images, set tags and categories for them etc.
2. Go to a particular album in your media library and click “Upload files to album” on the right. Then drag the files to the “Drag files here” field or click “upload photos manually”.