If you know the name of the component interface, you can easily find it in App Designer. Just press Ctrl+O or File > Open and search for it by name. But, what if you only know the name of the component that the component interface accesses?
You have to go to the database. Try this SQL (replacing <Component_Name> with your actual component) :
SELECT * FROM PSBCDEFN WHERE BCPGNAME = '<Component_Name>'