How to customize screen in agentry

Hi Experts,

I am new to SMP, I would require some support for a requirement.

We are using SMP 3.0 SP03 and now upgrading to SP05 PL01 level and workmanager 6.1 & iphone as end client.

We already have app to create notification & deployed in production and users are utilizing it.

Now, I need to customize the screen to add drop down values of workcenter.

Can any one please suggest what all things i need to do and development procedure.

Thanks in advance.

Regards,

Thulasiram