Obtain pumpkin seeds by finding pumpkins in villages, woodland mansions, shipwrecks, or pillager outposts, then crafting them into seeds
Till grass or dirt with a hoe to create farmland
Place water nearby to hydrate the farmland
Plant the pumpkin seeds on the farmland
Leave an empty dirt, grass, farmland, or path block next to each pumpkin stem for the pumpkin to grow onto
Keep the stem area lit to help growth
Wait for the stem to mature and produce pumpkins on adjacent empty blocks
Use a hoe, axe, or hand to break the pumpkin for harvesting
Replant or keep the stem to continue producing more pumpkins
Use bone meal on the stem to speed up growth
Use multiple stems with multiple empty adjacent blocks for a larger pumpkin farm