You must hold the portal role GP Business Expert, or have the relevant permissions to work with Guided Procedures (GP) design time.
More information: Setting Up Portal Roles
...
1. Launch GP design time, as described in Launching Guided Procedures (GP) Design Time.
2. Choose Create Callable Object from the contextual panel.
3. In the Basic Data screen, enter the following values for the required parameters:
¡ Type – select User Interface → Web Dynpro Component (GP Interface)
¡ Name –User Details, for example
¡ Description –Display user details, for example
¡ Original Language – select English
¡ Folder – choose any folder in the gallery
4. Choose Next to open the Define Object screen.
Select Web Dynpro component CUserDetails.
If you have created entries in the message pool for CO_NAME and CO_DESCRIPTION parameters, you will see the texts in the text box on the right-hand side of the screen.
5. Choose Next to open the Define Input screen.
The system displays the input parameter User ID that you have defined into the component implementation. The name of the parameter is localized using the Web Dynpro message pool.
6. Choose Next to open the Define Output screen.
The system displays the output parameters that you have defined in the component implementation. The names of the parameters are localized using the Web Dynpro message pool.
7. Choose Next, and then Finish and Open.
You have opened the callable object design time. Now you can test and activate the object.
More information: Testing and Activating the Callable Object.