Solution

your error is because on the line above 10, you have indented @client.event, this is wrong. Try this code.

@client.event   # unindented
async def on_message(message):
  if message.author == client.user:
    return

you also have multiple indentation errors. Your overall code should look like this.

import discord

client = discord.Client()

@client.event
async def on_ready():
  print('We have logged in as {0.user}' .format (client)()
  
@client.event
async def on_message(message):
  if message.author == client.user:
    return

  msg = message.content
 
 
  if message.content.startswith ('!help'): # added colon, and unintended
    await message.channel.send('nah') # indented
 
 client.run(ODEwNDM3NzAzNzMyNjkwOTc1.YCjo7Q.WuS1lDpDMzuC23IP588brRHcVRc)

like that. Remember to only indent if you see a : on the line above.
Thats should work