Open the game menu
Click “Open to LAN” if you are in a single-player world
Turn “Allow Cheats” to ON
Click “Start LAN World”
Open the chat window
Type `/gamemode creative`
Press Enter
If cheats are already enabled, open chat and type `/gamemode creative`
On servers, use `/gamemode creative` if you have permission
On Bedrock Edition, use `/gamemode creative` in chat if cheats are enabled