please try after open custom management windows

hello i am a fellow rohan player who has played before but i am starting new again i bought a permanent custom from IM and i bought 3 trian's pattern that have VIT PSY AND INT when i try to wear them the game tells me please try after open custom management window can someone please advise where is this window?

Unequipped the costume, right click it, then there will be a window showing you the options. Click pattern management button. You can now place those stone in the sockets :D