Hi,
I think from step 2, you will just have to follow what you want from your ztransaction. Its like an recording. The example shows hows you can just initialize values in the starting fields. Its applicable to the initial screen with which the transaction opens.
In your custom transaction enter or the Green Button behavior might not be same as shown in the example T-Code. The idea is to exit the T-Code after the initial values are given, indicating end of recording that then takes us to the next screen.
Then we can do the rest with the default values and the fields. Hope that helps.
Cheers,
Arindam