Just use the ww lure from your inventory, like a normal item. For the love potion, I really don't remember, maybe from the witch, and if you don't find, just check the guide and discover it by yourself ^^
when in a fight you use it for your turn, each instance of it lasts 25 turns. you need 100 turns of it in affect to get 100% capture. so thats 5 uses to make sure you have 100 turns an have time to beat the enemy to capture it
