You can get the Android app from the Play Store now!
This is pretty easy!
For iOS, it’s a lot more complicated because you have to build it yourself right now.
There are instructions here:
Building and running iOS Client on your Phone Instructions
Post here if you run into any problems with the instructions.
These are very alpha right now – there are some pretty significant visual bugs in them. But we are working on them and you can try it out if you want to make mobile stuff on Castle.