More qualified people will chime in so I’ll be brief.
Currently you need to use the web interface. It’s kinda clunky, but very useable once you get the hang of it.
You can’t cut bitmaps. If you want to cut around a bitmap you will need to trace the outline as a vector.
It is helpful to do your order of operations by changing the colors of each step you want in your illustration program prior to exporting as SVG or PDF.