Take a range of column from STPO into a structure

Hello, i am new to SAP so not quite understand it yet, i want to take the first five column from the STPO table as an output when i insert a parent part that will take all the child component as display. But when i put it eg. 'STLTY TYPES STPO-STLTY' it says STPO not active although the table is active, why is it like that?