How do you fill a bottle in Skyward Sword? I'm trying to scoop up some water, and I can't figure out how to get the bottle equipped.
You can equip it like anything else in your bag, such as when you've got a new shield (hold - to select, press - to get it out.) and use it like an item. (Press A to use it after equiping.)
Finally figured it out.
Push and hold "-" and it will bring up a screen with all of your items in your pouch. You then use the wii-mote to select the item that you would like to equip by pressing 'A' and you can use it like any other item.
Just to clarify: to equip items, you have to press - (minus) when you're on the main walking-around screen, not when you're on the inventory screen (which you can separately access by pressing 1 [one]). It's confusing because there is also a pouch in the middle of the inventory, which you can also interact with using the - (minus) button.
Hold - then mouseover the desired item to equip (shield or bottle; medals are considered equipped if Link is carrying one and bags provide a passive storage bonus). Note that you don't have to equip a bottle to catch a fairy, you can use the Bug Catching Net instead.
To scoop up water, equip a bottle then press A while standing in the water.
If you are carrying the "Cursed Medal" in your pouch your pouch items are inaccessible. You must store the cursed medal at the claim check in the bazaar on skyloft.