Action name: PatchByte, PatchWordYou can modify the executable file and eventually generate a new file.
If you patch bytes, then you may enter multiple bytes. Follow this link to learn about format of the input string.
If this command is invoked when the debugger is active, then IDA will modify the memory and the database. If the database does not contain the patched bytes, then only the process memory will be modified.
You can create a difference file too.
Edit|Patch core submenu. How to Enter a Number.