Ok, so the next phase is to install app inventor software on my machine. 90Mb of download (my ISP won't like that), but it's a necessary evil.
Being a bit wary of working directly onto my phone, I've decided to start by using the emulator.
Phase 2 complete.
Phase 3 - so I worked through the Kitty tutorial and it worked :D The tutorial was excellent, but I did use the emulator and I think I ought to be brave enough to create it on my own phone.
My next plan is to use a photo of my own cat instead, so that it's personal, and then I'll do the last bit and actually add it to my phone, so that I can show it off to everyone. App designing here I come!!!