To upload the creative within Pexi you need a Pexi account and access to the correct advertiser. You can request a Pexi account via email@example.com. When you have access to Pexi you can upload the banner as a zip (zip the folder, not the files). If you include the IAB size within the filename Pexi will automatically detect and adjust the upload settings.
The swipecube works as a gallery for images similar to the mobile portrait slider. The difference is that in a swipecube images are positioned and rotated in such a way to create a 3d effect to resemble a cube.