Wher do I enter lines for a sensor in yaml file

[orange-assistant]

@Rob_Heselwood

sensor:
  platform: bh1750
  name: "BH1750 Illuminance"
  address: 0x23
  update_interval: 60s
  

  platform: bme280

This yaml should generate this error

@Rob_Heselwood

NFO Reading configuration /config/esphome/esphome.yaml…
ERROR Error while reading config: Invalid YAML syntax:

Duplicate key "platform"
  in "/config/esphome/esphome.yaml", line 17, column 3:
      platform: bme280
      ^
NOTE: Previous declaration here:
  in "/config/esphome/esphome.yaml", line 11, column 3:
      platform: bh1750
      ^

So all good I would say.

Best for you @Rob_Heselwood would be to spend like 5 or 10 minutes reading what YAML is and how it "works", some link was already posted earlier but feel free to use a search engine of your choice to gather more information

@Arh

may be worth reading this (disclaimer I have not read it all to confirm it is correct or useful)

What is YAML? A beginner's guide | CircleCI.

Beside if you need further help this post explains how to ask good questions

How to help us help you - or How to ask a good question