Players who jump back to Legends of Zelda: Skyward Sword HD will eagerly want them to fall into the hands of Slingshot. Through the campaign, it is basic equipment. The good news is that Slingshot will be rewarded from Buch in Faron Woods.
They will ask you to complete a task that involves finding some Kikwi, and when you track them all down, you can return to Bucha and get a Slingshot. All you have to do is check in at Kikwis, which you will find among the plants, and then report back to Buch.
Once you get the Slingshot, you will need to equip it by clicking the ZR button to bring up a menu of items. Select Slingshot and you will be able to shoot Blanket Seeds. Remember that you can only really use Slingshot when you shoot Deku Seed with it. You can find the Blanket seeds by mowing the grass and breaking the flowerpot, or you can buy them in the Bazaar if you wish.
The slingshot can be used to stun enemies, activate switches, and open new climbing paths by cutting down vineyards.