How to pick up things in minecraft pocket edition?

To use an apple you only have to put it on your hotbar and use it like you would a tool. This will cause you to eat it.

Picks:
Each material requires a specific pick. You can always use a higher level pickaxe to mine a lower material, but you must meet the minimum pick level to get the resource to drop a block you can pickup.

Each level of pickaxe has more endurance than the levels below it.

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Bare hands - Can mine dirt, sand, and gravel.

Wood Pickaxe - Can mine coal and stone, which drops as cobblestone. Smelt to cobblestone to turn it back to stone, but there are few recipes that need stone.

Stone Pickaxe (ie the pickaxe made of Cobblestone) - Can mine Iron.

Gold Pickaxe - This mines the same level as stone, but much faster. It also has the lowest endurance of any pick. This pick is *not* recommended, there are better uses for gold.

Iron Pickaxe - Can mine everything *except* Obsidian and Bedrock. Until you have a number of diamonds this should be your go-to pick.

Diamond Pickaxe - The highest level pickax. The Diamond Pick can mine everything except Bedrock (which is unbreakable). It also has significantly more endurance than the Iron Pick.

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Note that while you can use picks to acquire any block it is better to use the appropriate tool, as using any other tool causes the tool to break faster.

Shovel - Sand, Dirt, Gravel
Axe - Trees and Planks.
Pickaxe - See above.
Sword - Living things such as mobs and animals.