Except for villages, wheat doesn't naturally appear in the game on its own. Here are some steps for a very early-game wheat farm:
1. Break a bunch of [[Grass]] blocks to obtain seeds (they only drop occasionally)
2. Craft a [[Wooden Hoe]], and use it by right-clicking on dirt blocks near a source of water (i.e., within 4m of a water source block). These will turn into tilled dirt blocks.
3. Right-click the tilled dirt with the seeds, and tiny, immature wheat plants will appear. These will slowly grow when given enough light until they are completely mature.
4. Harvest the wheat by left-clicking the plant. Fully mature plants will drop a wheat item as well as some more seeds. Immature plants will only drop seeds.
5. Use the seeds you recover to re-plant your farm.