Open your Minecraft world
Choose where you want the door to go
Stand facing the block where the door will be placed
Make sure the space is clear for the door (2 blocks high)
Select a door item in your hotbar
Place the door by right-clicking (or using the use button) on the block
If needed, place it on the correct side by adjusting your position before placing
To open or close the door, right-click it (or use the use button)