If you followed it exactly and still can not create an aia on your deshtop, most probably, one of the following applies to your code:
1) You have coding errors in your blocks. In the Blocks editor, look in the lower left for the yellow and red triangle icons. If the red icon has a value larger than 0, you have a serious coding error. Find the block in your code that has a red triangle and fix it. Red triangles always inhibit creating an apk or running a project in the emulator or possibly creating an aia file. Yellow triangles are more forgiving, however, sometimes, these need to be fixed because they trip an internal warning and you do not get a compile, so fix the yellow triangles too.
2) Your source file (the aia file) is larger than the 5Mb limit allowed in AI2. You can program apps larger than 5Mb in the browser, but they will not compile and might not run in the emulator or save as an aia. In this case you need to reduce the size of your image and/or sound files. Most image files can be made quite small by resizing them using a photo manipulation program on your PC to less than 50Kb each.
3) You might have more than 10 Screens in your app. AI2 becomes unstable when more than ten screens are used.
4) You might have used a too large image as icon. Use a size of 48x48 px or 96x96px instead.
You need to tell us more about your problem in order for us to help if none of the above conditions is what is causing your problem.
Were you able to export the aia? If not what did you try and what happened?
Regards,
Steve