As of 3.2.0, Stick Nodes will no longer automatically find downloaded files in your /downloads/ folder. You must open the file with Stick Nodes explicitly for it to be moved into the correct folder.
Download a NODES (or STK) or ZIP file. When done, tap it and "Open With" > "Stick Nodes". See this image for an example.
Sounds: Download an MP3 file < 256kb. When done, tap it and "Open With" > "Stick Nodes"..
IOS 13+ How to download stickfigures & sounds:
If using Chrome or Firefox, download a NODES (or STK) or ZIP file, select the file and "Open in Stick Nodes" after finished downloading.
If using Safari, download a NODES (or STK) or ZIP file, follow these directions.
Ah, the top of the animation house, where South Park rubs elbows with surreal entertainment