1.) Log into the interface and click in the menu on "Files" => "Upload files".
2.) Just drop the files that should be uploaded via Drag & Drop from your PC into the white area, or just click into the white area to select the files from your PC. When you click on the button "Select files from Dropbox", you can also upload files that are saved on Dropbox.
3.) You can repeat this step several times, until all of your desired files are listed.
Tip: Press and hold the Ctrl key in order to select multiple files at once.
4.) The selected files are displayed with a small preview.
You can remove a single file from the list again by clicking on the "X" or you can empty the complete list by clicking on the button "Empty file list".
5.) When you're done with selecting your files, you can upload the files by clicking on "Upload selected files".
Now your files are uploaded to our servers and afterwards you can include them into your website.