From the home page top bar, select "Upload" >> "Images" >> "Compressed Uploader"
Select your "Project" from the drop down menu, then ensure "Prearchive" is selected and click on "Choose File" to select the file containing your DICOM images that you zipped in step 1. Finally click "Begin Upload". This may take a several minutes depending on the size of your session.
Once the image upload is complete, navigate to the prearchive by going to the top bar "Upload" >> "Go to Prearchive"