How do I edit screen items once I have created them?
Clicking on any item brings up a contextual menu. From here you can choose to edit the item, move it, copy it or edit the source code.
Can I edit pictures once I have uploaded them?
Yes - There is a built in picture editor in the image browser. Once you have selected your image, click on it and choose the edit icon (a rounded square with a pencil in the corner). Here you have many options to change your image including filters, frames, text input and many more.