Enter the transaction code PPCI
Enter a four digit infotype number (9nnn) and an infotype name.
In your case it would be '9004' and 'Site type and Industry'.
Select Field Infotype
Choose Infotype Create.
Choose Check environment to maintain the required entry in table T777I (Infotypes per object type).
Choose the Entry 'T777I' under the list of 'Table Entries' (This list is produced when you choose 'Check' on the First screen of the Transaction PPCI.
Press the 'Change' button and you will be taken to the 'Maintain Table Views' Transaction (SM30).
Press the Maintain button.
From the list of Infotypes locate the Custom Infotype that you have created and select the entry for that.
Click on the 'Time Constraint' folder appearing on the left hand corner of the screen.
The screen for Change View Time Constraint would appear.
In the object type field put in: O,P,S whatever is relevant to your requirement.
Also add the time constraint.
Save it and double click on the 'Infotypes per object type' folder (on the left hand side again).
Create a new entry here for your infotype and save it.
Come back to the Transaction PPCI and you are all set!
You have successfully created a Custom Infotype and can use the same through PO10.