In battle, click the teapot, and select the item. Then touch "use" and use it on a party member. outside of battle, wait for a while until your party members come up on the bottom right corner. select the blue box, and on the right, select "items". Then select use and use it like you would in battle
edit: nvm, just noticed you were talking about equipment. what you do is equip them in the menu, and go to equipment. select a party member. Click on weapon, hat, armor, etc. and then select the item you want to equip.
edit:Again, i just read your question differently -_- The effects may automatically occur or use them in the magic section. I have never tried to equip these, might try it myself.